refactor: Migrate database service to SQLModel and Alembic.

- Add SQLModel for type-safe database models
- Implement Alembic for schema migration management
- Create 7 migrations covering all existing schema changes
- Add automatic migration system that runs on startup
- Maintain backward compatibility with existing raw SQL queries
- Remove old manual migration system
- All tests pass (109 tests)

Benefits:
- Full type safety with Pydantic validation
- Version-controlled schema changes
- Automatic migration detection and application
- Better developer experience with typed models

alembic/README

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+Generic single-database configuration.

alembic/env.py

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+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config, pool
+
+from alembic import context
+from leggen.models.database import SQLModel
+from leggen.services.database import get_database_url
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Set the database URL from our configuration
+config.set_main_option("sqlalchemy.url", get_database_url())
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+target_metadata = SQLModel.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(connection=connection, target_metadata=target_metadata)
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

alembic/script.py.mako

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+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, Sequence[str], None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    ${downgrades if downgrades else "pass"}

alembic/versions/1ba02efe481c_migrate_to_composite_key.py

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+"""migrate_to_composite_key
+
+Migrate transactions table to use composite primary key (accountId, transactionId).
+
+Revision ID: 1ba02efe481c
+Revises: bf30246cb723
+Create Date: 2025-09-30 23:16:34.637762
+
+"""
+
+from typing import Sequence, Union
+
+from sqlalchemy import text
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "1ba02efe481c"
+down_revision: Union[str, Sequence[str], None] = "bf30246cb723"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Migrate to composite primary key."""
+    conn = op.get_bind()
+
+    # Check if migration is needed
+    result = conn.execute(
+        text("""
+        SELECT name FROM sqlite_master
+        WHERE type='table' AND name='transactions'
+    """)
+    )
+
+    if not result.fetchone():
+        return
+
+    # Create temporary table with new schema
+    op.execute("""
+        CREATE TABLE transactions_temp (
+            accountId TEXT NOT NULL,
+            transactionId TEXT NOT NULL,
+            internalTransactionId TEXT,
+            institutionId TEXT NOT NULL,
+            iban TEXT,
+            transactionDate DATETIME,
+            description TEXT,
+            transactionValue REAL,
+            transactionCurrency TEXT,
+            transactionStatus TEXT,
+            rawTransaction JSON NOT NULL,
+            PRIMARY KEY (accountId, transactionId)
+        )
+    """)
+
+    # Insert deduplicated data (keep most recent duplicate)
+    op.execute("""
+        INSERT INTO transactions_temp
+        SELECT
+            accountId,
+            json_extract(rawTransaction, '$.transactionId') as transactionId,
+            internalTransactionId,
+            institutionId,
+            iban,
+            transactionDate,
+            description,
+            transactionValue,
+            transactionCurrency,
+            transactionStatus,
+            rawTransaction
+        FROM (
+            SELECT *,
+                   ROW_NUMBER() OVER (
+                       PARTITION BY accountId, json_extract(rawTransaction, '$.transactionId')
+                       ORDER BY transactionDate DESC, rowid DESC
+                   ) as rn
+            FROM transactions
+            WHERE json_extract(rawTransaction, '$.transactionId') IS NOT NULL
+            AND accountId IS NOT NULL
+        ) WHERE rn = 1
+    """)
+
+    # Replace tables
+    op.execute("DROP TABLE transactions")
+    op.execute("ALTER TABLE transactions_temp RENAME TO transactions")
+
+    # Recreate indexes
+    op.create_index(
+        "idx_transactions_internal_id", "transactions", ["internalTransactionId"]
+    )
+    op.create_index("idx_transactions_date", "transactions", ["transactionDate"])
+    op.create_index(
+        "idx_transactions_account_date",
+        "transactions",
+        ["accountId", "transactionDate"],
+    )
+    op.create_index("idx_transactions_amount", "transactions", ["transactionValue"])
+
+
+def downgrade() -> None:
+    """Not implemented - would require changing primary key back."""

alembic/versions/4819c868ebc1_add_transaction_enrichments_table.py

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+"""add_transaction_enrichments_table
+
+Add transaction_enrichments table for storing enriched transaction data.
+
+Revision ID: 4819c868ebc1
+Revises: dd9f6a55604c
+Create Date: 2025-09-30 23:20:00.969614
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "4819c868ebc1"
+down_revision: Union[str, Sequence[str], None] = "dd9f6a55604c"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create transaction_enrichments table."""
+    op.create_table(
+        "transaction_enrichments",
+        sa.Column("accountId", sa.String(), nullable=False),
+        sa.Column("transactionId", sa.String(), nullable=False),
+        sa.Column("clean_name", sa.String(), nullable=True),
+        sa.Column("category", sa.String(), nullable=True),
+        sa.Column("logo_url", sa.String(), nullable=True),
+        sa.Column("created_at", sa.DateTime(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(), nullable=False),
+        sa.ForeignKeyConstraint(
+            ["accountId", "transactionId"],
+            ["transactions.accountId", "transactions.transactionId"],
+            ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint("accountId", "transactionId"),
+    )
+
+    # Create indexes
+    op.create_index(
+        "idx_transaction_enrichments_category", "transaction_enrichments", ["category"]
+    )
+    op.create_index(
+        "idx_transaction_enrichments_clean_name",
+        "transaction_enrichments",
+        ["clean_name"],
+    )
+
+
+def downgrade() -> None:
+    """Drop transaction_enrichments table."""
+    op.drop_table("transaction_enrichments")

alembic/versions/be8d5807feca_add_display_name_column.py

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+"""add_display_name_column
+
+Add display_name column to accounts table.
+
+Revision ID: be8d5807feca
+Revises: 1ba02efe481c
+Create Date: 2025-09-30 23:16:34.929968
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "be8d5807feca"
+down_revision: Union[str, Sequence[str], None] = "1ba02efe481c"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Add display_name column to accounts table."""
+    with op.batch_alter_table("accounts", schema=None) as batch_op:
+        batch_op.add_column(sa.Column("display_name", sa.String(), nullable=True))
+
+
+def downgrade() -> None:
+    """Remove display_name column."""
+    with op.batch_alter_table("accounts", schema=None) as batch_op:
+        batch_op.drop_column("display_name")

alembic/versions/bf30246cb723_migrate_balance_timestamps.py

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+"""migrate_balance_timestamps
+
+Convert Unix timestamps to datetime strings in balances table.
+
+Revision ID: bf30246cb723
+Revises: de8bfb1169d4
+Create Date: 2025-09-30 23:14:03.128959
+
+"""
+
+from datetime import datetime
+from typing import Sequence, Union
+
+from sqlalchemy import text
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "bf30246cb723"
+down_revision: Union[str, Sequence[str], None] = "de8bfb1169d4"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Convert all Unix timestamps to datetime strings."""
+    conn = op.get_bind()
+
+    # Get all balances with REAL timestamps
+    result = conn.execute(
+        text("""
+        SELECT id, timestamp
+        FROM balances
+        WHERE typeof(timestamp) = 'real'
+        ORDER BY id
+    """)
+    )
+
+    unix_records = result.fetchall()
+
+    if not unix_records:
+        return
+
+    # Convert and update in batches
+    for record_id, unix_timestamp in unix_records:
+        try:
+            # Convert Unix timestamp to datetime string
+            dt_string = datetime.fromtimestamp(float(unix_timestamp)).isoformat()
+
+            # Update the record
+            conn.execute(
+                text("UPDATE balances SET timestamp = :dt WHERE id = :id"),
+                {"dt": dt_string, "id": record_id},
+            )
+        except Exception:
+            continue
+
+    conn.commit()
+
+
+def downgrade() -> None:
+    """Not implemented - converting back would lose precision."""

alembic/versions/dd9f6a55604c_add_logo_column.py

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+"""add_logo_column
+
+Add logo column to accounts table.
+
+Revision ID: dd9f6a55604c
+Revises: f854fd498a6e
+Create Date: 2025-09-30 23:16:35.530858
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "dd9f6a55604c"
+down_revision: Union[str, Sequence[str], None] = "f854fd498a6e"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Add logo column to accounts table."""
+    with op.batch_alter_table("accounts", schema=None) as batch_op:
+        batch_op.add_column(sa.Column("logo", sa.String(), nullable=True))
+
+
+def downgrade() -> None:
+    """Remove logo column."""
+    with op.batch_alter_table("accounts", schema=None) as batch_op:
+        batch_op.drop_column("logo")

alembic/versions/de8bfb1169d4_create_initial_tables.py

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+"""create_initial_tables
+
+Revision ID: de8bfb1169d4
+Revises:
+Create Date: 2025-09-30 23:09:24.255875
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "de8bfb1169d4"
+down_revision: Union[str, Sequence[str], None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create initial database tables."""
+    # Create accounts table
+    op.create_table(
+        "accounts",
+        sa.Column("id", sa.String(), nullable=False),
+        sa.Column("institution_id", sa.String(), nullable=False),
+        sa.Column("status", sa.String(), nullable=False),
+        sa.Column("iban", sa.String(), nullable=True),
+        sa.Column("name", sa.String(), nullable=True),
+        sa.Column("currency", sa.String(), nullable=True),
+        sa.Column("created", sa.DateTime(), nullable=False),
+        sa.Column("last_accessed", sa.DateTime(), nullable=True),
+        sa.Column("last_updated", sa.DateTime(), nullable=True),
+        sa.PrimaryKeyConstraint("id"),
+    )
+    op.create_index("idx_accounts_institution_id", "accounts", ["institution_id"])
+    op.create_index("idx_accounts_status", "accounts", ["status"])
+
+    # Create balances table
+    op.create_table(
+        "balances",
+        sa.Column("id", sa.Integer(), autoincrement=True, nullable=False),
+        sa.Column("account_id", sa.String(), nullable=False),
+        sa.Column("bank", sa.String(), nullable=False),
+        sa.Column("status", sa.String(), nullable=False),
+        sa.Column("iban", sa.String(), nullable=False),
+        sa.Column("amount", sa.Float(), nullable=False),
+        sa.Column("currency", sa.String(), nullable=False),
+        sa.Column("type", sa.String(), nullable=False),
+        sa.Column("timestamp", sa.DateTime(), nullable=False),
+        sa.PrimaryKeyConstraint("id"),
+    )
+    op.create_index("idx_balances_account_id", "balances", ["account_id"])
+    op.create_index("idx_balances_timestamp", "balances", ["timestamp"])
+    op.create_index(
+        "idx_balances_account_type_timestamp",
+        "balances",
+        ["account_id", "type", "timestamp"],
+    )
+
+    # Create transactions table (old schema with internalTransactionId as PK)
+    op.create_table(
+        "transactions",
+        sa.Column("accountId", sa.String(), nullable=False),
+        sa.Column("transactionId", sa.String(), nullable=False),
+        sa.Column("internalTransactionId", sa.String(), nullable=True),
+        sa.Column("institutionId", sa.String(), nullable=False),
+        sa.Column("iban", sa.String(), nullable=True),
+        sa.Column("transactionDate", sa.DateTime(), nullable=True),
+        sa.Column("description", sa.String(), nullable=True),
+        sa.Column("transactionValue", sa.Float(), nullable=True),
+        sa.Column("transactionCurrency", sa.String(), nullable=True),
+        sa.Column("transactionStatus", sa.String(), nullable=True),
+        sa.Column("rawTransaction", sa.JSON(), nullable=False),
+        sa.PrimaryKeyConstraint("internalTransactionId"),
+    )
+    op.create_index(
+        "idx_transactions_internal_id", "transactions", ["internalTransactionId"]
+    )
+    op.create_index("idx_transactions_date", "transactions", ["transactionDate"])
+    op.create_index(
+        "idx_transactions_account_date",
+        "transactions",
+        ["accountId", "transactionDate"],
+    )
+    op.create_index("idx_transactions_amount", "transactions", ["transactionValue"])
+
+
+def downgrade() -> None:
+    """Drop initial tables."""
+    op.drop_table("transactions")
+    op.drop_table("balances")
+    op.drop_table("accounts")

alembic/versions/f854fd498a6e_add_sync_operations_table.py

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+"""add_sync_operations_table
+
+Add sync_operations table for tracking synchronization operations.
+
+Revision ID: f854fd498a6e
+Revises: be8d5807feca
+Create Date: 2025-09-30 23:16:35.229062
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "f854fd498a6e"
+down_revision: Union[str, Sequence[str], None] = "be8d5807feca"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create sync_operations table."""
+    op.create_table(
+        "sync_operations",
+        sa.Column("id", sa.Integer(), autoincrement=True, nullable=False),
+        sa.Column("started_at", sa.DateTime(), nullable=False),
+        sa.Column("completed_at", sa.DateTime(), nullable=True),
+        sa.Column("success", sa.Boolean(), nullable=True),
+        sa.Column(
+            "accounts_processed", sa.Integer(), nullable=False, server_default="0"
+        ),
+        sa.Column(
+            "transactions_added", sa.Integer(), nullable=False, server_default="0"
+        ),
+        sa.Column(
+            "transactions_updated", sa.Integer(), nullable=False, server_default="0"
+        ),
+        sa.Column("balances_updated", sa.Integer(), nullable=False, server_default="0"),
+        sa.Column("duration_seconds", sa.Float(), nullable=True),
+        sa.Column("errors", sa.String(), nullable=True),
+        sa.Column("logs", sa.String(), nullable=True),
+        sa.Column("trigger_type", sa.String(), nullable=False, server_default="manual"),
+        sa.PrimaryKeyConstraint("id"),
+    )
+
+    # Create indexes
+    op.create_index("idx_sync_operations_started_at", "sync_operations", ["started_at"])
+    op.create_index("idx_sync_operations_success", "sync_operations", ["success"])
+    op.create_index(
+        "idx_sync_operations_trigger_type", "sync_operations", ["trigger_type"]
+    )
+
+
+def downgrade() -> None:
+    """Drop sync_operations table."""
+    op.drop_table("sync_operations")