feat(notifications): disable realtime/WebSocket entirely — REST fetch + focus refresh only

- remove postgres_changes .channel().subscribe() from useNotifications
- notifications now load via REST on mount and refresh on tab focus
- eliminates WS retry hangs (30-40s stalls) from dead realtime container;
  web-push (Push API) is unaffected and works independently

src/hooks/useNotifications.js

@@ -31,50 +31,19 @@ export function useNotifications(userId) {
     fetchNotifications();
   }, [fetchNotifications]);
 
-  // Realtime subscription
+  // NOTE: realtime (WebSocket) subscription intentionally removed (2026-08).
+  // The supabase realtime container kept dying and the client hung in WS retry
+  // loops (30-40s stalls on open). Notifications now update via REST fetch on
+  // page load / focus only — see handleFocus below for refresh on tab focus.
+
+  // Refresh notifications when the tab regains focus so the unread badge stays
+  // reasonably fresh without a live WebSocket connection.
   React.useEffect(() => {
     if (!hasSupabaseConfig || !userId) return;
-
-    const channel = supabase
-      .channel(`notifications:${userId}`)
-      .on(
-        "postgres_changes",
-        {
-          event: "INSERT",
-          schema: "public",
-          table: "notifications",
-          filter: `user_id=eq.${userId}`,
-        },
-        (payload) => {
-          const newNotif = payload.new;
-          setNotifications((prev) => [newNotif, ...prev].slice(0, 50));
-          setUnreadCount((prev) => prev + 1);
-        }
-      )
-      .on(
-        "postgres_changes",
-        {
-          event: "UPDATE",
-          schema: "public",
-          table: "notifications",
-          filter: `user_id=eq.${userId}`,
-        },
-        (payload) => {
-          const updated = payload.new;
-          setNotifications((prev) =>
-            prev.map((n) => (n.id === updated.id ? updated : n))
-          );
-          setUnreadCount((prev) =>
-            Math.max(0, prev + (updated.read ? -1 : 0) + (prev === 0 && !updated.read ? 1 : 0))
-          );
-        }
-      )
-      .subscribe();
-
-    return () => {
-      supabase.removeChannel(channel);
-    };
-  }, [userId]);
+    const handleFocus = () => fetchNotifications();
+    window.addEventListener("focus", handleFocus);
+    return () => window.removeEventListener("focus", handleFocus);
+  }, [fetchNotifications, userId]);
 
   // Fix unread count: always recalculate from notifications
   React.useEffect(() => {