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>

PROJECT.md

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+# Leggen Web Transformation Project
+
+## Overview
+Transform leggen from CLI-only to web application with FastAPI backend (`leggend`) and SvelteKit frontend (`leggen-web`).
+
+## Progress Tracking
+
+### ✅ Phase 1: FastAPI Backend (`leggend`)
+
+#### 1.1 Core Structure
+- [x] Create directory structure (`leggend/`, `api/`, `services/`, etc.)
+- [x] Add FastAPI dependencies to pyproject.toml
+- [x] Create configuration management system
+- [x] Set up FastAPI main application
+- [x] Create Pydantic models for API responses
+
+#### 1.2 API Endpoints
+- [x] Banks API (`/api/v1/banks/`)
+  - [x] `GET /institutions` - List available banks
+  - [x] `POST /connect` - Connect to bank
+  - [x] `GET /status` - Bank connection status
+- [x] Accounts API (`/api/v1/accounts/`)
+  - [x] `GET /` - List all accounts
+  - [x] `GET /{id}/balances` - Account balances
+  - [x] `GET /{id}/transactions` - Account transactions
+- [x] Sync API (`/api/v1/sync/`)
+  - [x] `POST /` - Trigger manual sync
+  - [x] `GET /status` - Sync status
+- [x] Notifications API (`/api/v1/notifications/`)
+  - [x] `GET/POST/PUT /settings` - Manage notification settings
+
+#### 1.3 Background Jobs
+- [x] Implement APScheduler for sync scheduling
+- [x] Replace Ofelia with internal Python scheduler
+- [x] Migrate existing sync logic from CLI
+
+### ⏳ Phase 2: SvelteKit Frontend (`leggen-web`)
+
+#### 2.1 Project Setup
+- [ ] Create SvelteKit project structure
+- [ ] Set up API client for backend communication
+- [ ] Design component architecture
+
+#### 2.2 UI Components
+- [ ] Dashboard with account overview
+- [ ] Bank connection wizard
+- [ ] Transaction history and filtering
+- [ ] Settings management
+- [ ] Real-time sync status
+
+### ✅ Phase 3: CLI Refactoring
+
+#### 3.1 API Client Integration
+- [x] Create HTTP client for FastAPI calls
+- [x] Refactor existing commands to use APIs
+- [x] Maintain CLI user experience
+- [x] Add API URL configuration option
+
+### ✅ Phase 4: Docker & Deployment
+
+#### 4.1 Container Setup
+- [x] Create Dockerfile for `leggend` service
+- [x] Update docker-compose.yml with `leggend` service
+- [x] Remove Ofelia dependency (scheduler now internal)
+- [ ] Create Dockerfile for `leggen-web` (deferred - not implementing web UI yet)
+
+## Current Status
+**Active Phase**: Phase 2 - CLI Integration Complete
+**Last Updated**: 2025-09-01
+**Completion**: ~80% (FastAPI backend and CLI refactoring complete)
+
+## Next Steps (Future Enhancements)
+1. Implement SvelteKit web frontend
+2. Add real-time WebSocket support for sync status
+3. Implement user authentication and multi-user support
+4. Add more comprehensive error handling and logging
+5. Implement database migrations for schema changes
+
+## Recent Achievements
+- ✅ Complete FastAPI backend with all major endpoints
+- ✅ Configurable background job scheduler (replaces Ofelia)
+- ✅ CLI successfully refactored to use API endpoints
+- ✅ Docker configuration updated for new architecture
+- ✅ Maintained backward compatibility and user experience
+
+## Architecture Decisions
+- **FastAPI**: For high-performance async API backend
+- **APScheduler**: For internal job scheduling (replacing Ofelia)
+- **SvelteKit**: For modern, reactive frontend
+- **Existing Logic**: Reuse all business logic from current CLI commands
+- **Configuration**: Centralize in `leggend` service, maintain TOML compatibility