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>

CLAUDE.md

@@ -0,0 +1,69 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Leggen is an Open Banking CLI tool built in Python that connects to banks using the GoCardless Open Banking API. It allows users to sync bank transactions to SQLite/MongoDB databases, visualize data with NocoDB, and send notifications based on transaction filters.
+
+## Development Commands
+
+- **Install dependencies**: `uv sync` (uses uv package manager)
+- **Run locally**: `uv run leggen --help`
+- **Lint code**: `ruff check` and `ruff format` (configured in pyproject.toml)
+- **Build Docker image**: `docker build -t leggen .`
+- **Run with Docker Compose**: `docker compose up -d`
+
+## Architecture
+
+### Core Structure
+- `leggen/main.py` - Main CLI entry point using Click framework with custom command loading
+- `leggen/commands/` - CLI command implementations (balances, sync, transactions, etc.)
+- `leggen/utils/` - Core utilities for authentication, database operations, network requests, and notifications
+- `leggen/database/` - Database adapters for SQLite and MongoDB
+- `leggen/notifications/` - Discord and Telegram notification handlers
+
+### Key Components
+
+**Configuration System**:
+- Uses TOML configuration files (default: `~/.config/leggen/config.toml`)
+- Configuration loaded via `leggen/utils/config.py`
+- Supports GoCardless API credentials, database settings, and notification configurations
+
+**Authentication & API**:
+- GoCardless Open Banking API integration in `leggen/utils/gocardless.py`
+- Token-based authentication via `leggen/utils/auth.py`
+- Network utilities in `leggen/utils/network.py`
+
+**Database Operations**:
+- Dual database support: SQLite (`database/sqlite.py`) and MongoDB (`database/mongo.py`)
+- Transaction persistence and balance tracking via `utils/database.py`
+- Data storage patterns follow bank account and transaction models
+
+**Command Architecture**:
+- Dynamic command loading system in `main.py` with support for command groups
+- Commands organized as modules with individual click decorators
+- Bank management commands grouped under `commands/bank/`
+
+### Data Flow
+1. Configuration loaded from TOML file
+2. GoCardless API authentication and bank requisition management
+3. Account and transaction data retrieval from banks
+4. Data persistence to configured databases (SQLite/MongoDB)
+5. Optional notifications sent via Discord/Telegram based on filters
+6. Data visualization available through NocoDB integration
+
+## Docker & Deployment
+
+The project uses multi-stage Docker builds with uv for dependency management. The compose.yml includes:
+- Main leggen service with sync scheduling via Ofelia
+- NocoDB for data visualization
+- Optional MongoDB with mongo-express admin interface
+
+## Configuration Requirements
+
+All operations require a valid `config.toml` file with GoCardless API credentials. The configuration structure includes sections for:
+- `[gocardless]` - API credentials and endpoint
+- `[database]` - Storage backend selection
+- `[notifications]` - Discord/Telegram webhook settings
+- `[filters]` - Transaction matching patterns for notifications