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/notifications.py

@@ -0,0 +1,47 @@
+from typing import Dict, Any, Optional, List
+
+from pydantic import BaseModel
+
+
+class DiscordConfig(BaseModel):
+    """Discord notification configuration"""
+    webhook: str
+    enabled: bool = True
+
+
+class TelegramConfig(BaseModel):
+    """Telegram notification configuration"""
+    token: str
+    chat_id: int
+    enabled: bool = True
+
+
+class NotificationFilters(BaseModel):
+    """Notification filters configuration"""
+    case_insensitive: Dict[str, str] = {}
+    case_sensitive: Optional[Dict[str, str]] = None
+    amount_threshold: Optional[float] = None
+    keywords: List[str] = []
+
+
+class NotificationSettings(BaseModel):
+    """Complete notification settings"""
+    discord: Optional[DiscordConfig] = None
+    telegram: Optional[TelegramConfig] = None
+    filters: NotificationFilters = NotificationFilters()
+
+
+class NotificationTest(BaseModel):
+    """Test notification request"""
+    service: str  # "discord" or "telegram"
+    message: str = "Test notification from Leggen"
+
+
+class NotificationHistory(BaseModel):
+    """Notification history entry"""
+    id: str
+    service: str
+    message: str
+    status: str  # "sent", "failed"
+    sent_at: str
+    error: Optional[str] = None