fix: resolve pylint and type-checking issues

- Fix return type annotation in SetupRedirectMiddleware.dispatch() to use Response instead of RedirectResponse
- Replace broad 'except Exception' with specific exception types (FileNotFoundError, ValueError, OSError, etc.)
- Rename AppConfig.validate() to validate_config() to avoid shadowing BaseModel.validate()
- Fix ValidationResult.errors field to use List[str] with default_factory
- Add pylint disable comments for intentional broad exception catches during shutdown
- Rename lifespan parameter to _application to indicate unused variable
- Update all callers to use new validate_config() method name

src/server/fastapi_app.py

@@ -43,8 +43,13 @@ from src.server.services.websocket_service import get_websocket_service
 
 
 @asynccontextmanager
-async def lifespan(app: FastAPI):
-    """Manage application lifespan (startup and shutdown)."""
+async def lifespan(_application: FastAPI):
+    """Manage application lifespan (startup and shutdown).
+    
+    Args:
+        _application: The FastAPI application instance (unused but required
+            by the lifespan protocol).
+    """
     # Setup logging first with DEBUG level
     logger = setup_logging(log_level="DEBUG")
     
@@ -72,8 +77,11 @@ async def lifespan(app: FastAPI):
             )
             
             # Sync anime_directory from config.json to settings
-            if config.other and config.other.get("anime_directory"):
-                settings.anime_directory = str(config.other["anime_directory"])
+            # config.other is Dict[str, object] - pylint doesn't infer this
+            other_settings = dict(config.other) if config.other else {}
+            if other_settings.get("anime_directory"):
+                anime_dir = other_settings["anime_directory"]
+                settings.anime_directory = str(anime_dir)
                 logger.info(
                     "Loaded anime_directory from config: %s",
                     settings.anime_directory
@@ -82,7 +90,7 @@ async def lifespan(app: FastAPI):
                 logger.debug(
                     "anime_directory not found in config.other"
                 )
-        except Exception as e:
+        except (OSError, ValueError, KeyError) as e:
             logger.warning("Failed to load config from config.json: %s", e)
 
         # Initialize progress service with event subscription
@@ -131,7 +139,7 @@ async def lifespan(app: FastAPI):
                     "Download service initialization skipped - "
                     "anime directory not configured"
                 )
-        except Exception as e:
+        except (OSError, RuntimeError, ValueError) as e:
             logger.warning("Failed to initialize download service: %s", e)
             # Continue startup - download service can be initialized later
 
@@ -152,12 +160,14 @@ async def lifespan(app: FastAPI):
     
     # Shutdown download service and its thread pool
     try:
-        from src.server.services.download_service import _download_service_instance
+        from src.server.services.download_service import (  # noqa: E501
+            _download_service_instance,
+        )
         if _download_service_instance is not None:
             logger.info("Stopping download service...")
             await _download_service_instance.stop()
             logger.info("Download service stopped successfully")
-    except Exception as e:
+    except Exception as e:  # pylint: disable=broad-exception-caught
         logger.error("Error stopping download service: %s", e, exc_info=True)
     
     # Close database connections
@@ -165,7 +175,7 @@ async def lifespan(app: FastAPI):
         from src.server.database.connection import close_db
         await close_db()
         logger.info("Database connections closed")
-    except Exception as e:
+    except Exception as e:  # pylint: disable=broad-exception-caught
         logger.error("Error closing database: %s", e, exc_info=True)
     
     logger.info("FastAPI application shutdown complete")