feat: implement hybrid database architecture and frontend encryption

- Add PostgreSQL + SQLite hybrid database support with automatic switching
- Implement frontend AES-GCM + RSA-OAEP encryption for sensitive data
- Add comprehensive DatabaseInterface with all required methods
- Fix compilation issues with interface consistency
- Update all database method signatures to use DatabaseInterface
- Add missing UpdateTraderInitialBalance method to PostgreSQL implementation
- Integrate RSA public key distribution via /api/config endpoint
- Add frontend crypto service with proper error handling
- Support graceful degradation between encrypted and plaintext transmission
- Add directory creation for RSA keys and PEM parsing fixes
- Test both SQLite and PostgreSQL modes successfully

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

Co-Authored-By: tinkle-community <tinklefund@gmail.com>

config.json.example

@@ -20,5 +20,8 @@
   "max_daily_loss": 10.0,
   "max_drawdown": 20.0,
   "stop_trading_minutes": 60,
-  "jwt_secret": "Qk0kAa+d0iIEzXVHXbNbm+UaN3RNabmWtH8rDWZ5OPf+4GX8pBflAHodfpbipVMyrw1fsDanHsNBjhgbDeK9Jg=="
+  "jwt_secret": "Qk0kAa+d0iIEzXVHXbNbm+UaN3RNabmWtH8rDWZ5OPf+4GX8pBflAHodfpbipVMyrw1fsDanHsNBjhgbDeK9Jg==",
+  "log": {
+    "level": "info"
+  }
 }