feat: Transform to web architecture with FastAPI backend

This major update transforms leggen from CLI-only to a web-ready
architecture while maintaining full CLI compatibility.

New Features:
- FastAPI backend service (leggend) with comprehensive REST API
- Background job scheduler with configurable cron (replaces Ofelia)
- All CLI commands refactored to use API endpoints
- Docker configuration updated for new services
- API client with health checks and error handling

API Endpoints:
- /api/v1/banks/* - Bank connections and institutions
- /api/v1/accounts/* - Account management and balances
- /api/v1/transactions/* - Transaction retrieval with filtering
- /api/v1/sync/* - Manual sync and scheduler configuration
- /api/v1/notifications/* - Notification settings management

CLI Enhancements:
- New --api-url option and LEGGEND_API_URL environment variable
- Enhanced sync command with --wait and --force options
- Improved transactions command with --full and --limit options
- Automatic fallback and health checking

Breaking Changes:
- compose.yml structure updated (leggend service added)
- Ofelia scheduler removed (internal scheduler used instead)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

leggend/api/models/banks.py

@@ -0,0 +1,52 @@
+from datetime import datetime
+from typing import List, Optional
+
+from pydantic import BaseModel
+
+
+class BankInstitution(BaseModel):
+    """Bank institution model"""
+    id: str
+    name: str
+    bic: Optional[str] = None
+    transaction_total_days: int
+    countries: List[str]
+    logo: Optional[str] = None
+
+
+class BankConnectionRequest(BaseModel):
+    """Request to connect to a bank"""
+    institution_id: str
+    redirect_url: Optional[str] = "http://localhost:8000/"
+
+
+class BankRequisition(BaseModel):
+    """Bank requisition/connection model"""
+    id: str
+    institution_id: str
+    status: str
+    status_display: Optional[str] = None
+    created: datetime
+    link: str
+    accounts: List[str] = []
+    
+    class Config:
+        json_encoders = {
+            datetime: lambda v: v.isoformat()
+        }
+
+
+class BankConnectionStatus(BaseModel):
+    """Bank connection status response"""
+    bank_id: str
+    bank_name: str
+    status: str
+    status_display: str
+    created_at: datetime
+    requisition_id: str
+    accounts_count: int
+    
+    class Config:
+        json_encoders = {
+            datetime: lambda v: v.isoformat()
+        }