Run session reconnect asynchronously in FletAppManager

Session reconnect now uses an async task to avoid blocking the websocket receive loop with user handlers. Errors during reconnect are logged and reported to the session if possible.

Author: FeodorFitsner

sdk/python/packages/flet-web/src/flet_web/fastapi/flet_app_manager.py

@@ -81,7 +81,27 @@ async def reconnect_session(self, session_id: str, conn: Connection):
         logger.info(f"Session reconnected: {session_id}")
         if session_id in self.__sessions:
             session = self.__sessions[session_id]
-            await session.connect(conn)
+
+            # Run connect asynchronously so websocket receive loop isn't blocked by
+            # user handlers (e.g., on_connect invoking _invoke_method).
+
+            async def _connect():
+                try:
+                    await session.connect(conn)
+                except Exception as e:
+                    logger.error(
+                        f"Unhandled error reconnecting session {session_id}: {e}",
+                        exc_info=True,
+                    )
+                    try:
+                        session.error(str(e))
+                    except Exception:
+                        logger.error(
+                            "Failed to report reconnect error to session",
+                            exc_info=True,
+                        )
+
+            asyncio.create_task(_connect())
         else:
             raise RuntimeError(f"Session has expired or not found: {session_id}")