fix(tests): reliable SecurityMiddleware state reset via app.state reference

- Store direct reference to SecurityMiddleware instance in app.state._security_middleware
  immediately at module load time in main.py (before middleware_stack is built)
- Rewrite conftest.py _reset_all() to use app.state._security_middleware instead of
  fragile middleware stack traversal that failed before the first request was made
- Set explicit client=('127.0.0.1', 50000) on ASGITransport across all test files
  to ensure guard-core always sees a valid IP and can ban/track it correctly

app/main.py

@@ -56,9 +56,11 @@ config = SecurityConfig(
 )
 guard_deco = SecurityDecorator(config)
 
+_security_middleware = SecurityMiddleware(app.router, config=config)
 app.add_middleware(SecurityMiddleware, config=config)
 app.add_middleware(RequestLoggingMiddleware)
 app.state.guard_decorator = guard_deco
+app.state._security_middleware = _security_middleware
 mongo_worker = MongoWorker()
 _rabbit_worker: Optional[RabbitWorker] = None