feat(api): Add endpoints for webpanel decoy management using background tasks

- Add POST `/api/v1/config/hysteria/webpanel/decoy/setup` endpoint to configure the decoy site.
- Add POST `/api/v1/config/hysteria/webpanel/decoy/stop` endpoint to remove the decoy site configuration.
- Implement `BackgroundTasks` for both endpoints to prevent Caddy service restarts from interrupting the API response.
- Add `SetupDecoyRequest` Pydantic schema for the setup endpoint payload.

core/scripts/webpanel/config/config.py

@@ -10,6 +10,7 @@ class Configs(BaseSettings):
     API_TOKEN: str
     EXPIRATION_MINUTES: int
     ROOT_PATH: str
+    DECOY_PATH: str | None = None
 
     class Config:
         env_file = '.env'