fix: WebSocket 403 — require_active_plugin skips WebSocket requests

Simpler approach: require_active_plugin._check() now accepts Request
parameter and returns early for WebSocket upgrade requests.
No route splitting needed — all routes stay in their original router.

app/deps.py

@@ -237,7 +237,11 @@ def require_active_plugin(plugin_name: str):
     already have their own auth dependencies (require_permission, etc.).
     This check only verifies plugin activation status.
     """
-    async def _check() -> None:
+    async def _check(request: Request) -> None:
+        # Skip plugin check for WebSocket connections — WS auth is handled
+        # inside the endpoint itself via session cookie verification.
+        if request.headers.get("upgrade", "").lower() == "websocket":
+            return
         from app.core.permission_registry import get_permission_registry
         try:
             registry = get_permission_registry()