refactor: optimize middleware with pure ASGI implementation and enhance security measures

- Replace BaseHTTPMiddleware with pure ASGI implementation in plugin middleware for better streaming response handling
- Add trusted proxy count configuration for client IP extraction in reverse proxy environments
- Implement audit log cleanup scheduler with configurable retention period
- Replace plaintext token logging with SHA256 hash fingerprints for security
- Fix database session lifecycle management in middleware
- Improve request tracing and error logging throughout the system
- Add comprehensive tests for pipeline architecture

src/api/admin/api_keys/routes.py

@@ -223,7 +223,7 @@ class AdminCreateStandaloneKeyAdapter(AdminApiAdapter):
             allowed_providers=self.key_data.allowed_providers,
             allowed_api_formats=self.key_data.allowed_api_formats,
             allowed_models=self.key_data.allowed_models,
-            rate_limit=self.key_data.rate_limit or 100,
+            rate_limit=self.key_data.rate_limit,  # None 表示不限制
             expire_days=self.key_data.expire_days,
             initial_balance_usd=self.key_data.initial_balance_usd,
             is_standalone=True,  # 标记为独立Key