feat: production branch with deploy config for baota panel

- Add deploy/ directory with production env, supervisor, nginx, migration configs
- Include all latest features: admin management, feedback, footer with ICP/beian
- Database: foreign_trade (PostgreSQL), user: foreign_trade
- Frontend: trade.yuzhiran.com, backend proxy via Nginx

backend/app/models/__init__.py

@@ -10,6 +10,7 @@ from .subscription import Subscription
 from .preference import PreferenceAnalysis, MarketingEffect
 from .device import Device
 from .followup import FollowupStrategy, FollowupLog
+from .system_config import SystemConfig
 
 __all__ = [
     "User", "Product",
@@ -24,4 +25,5 @@ __all__ = [
     "PreferenceAnalysis", "MarketingEffect",
     "Device",
     "FollowupStrategy", "FollowupLog",
+    "SystemConfig",
 ]