fix: improve error handling and stability - no logout on transient errors, add ErrorBoundary, global error logging

frontend/src/hooks/useAuth.ts

@@ -4,14 +4,19 @@ import { useCurrentUser } from '@/api/hooks';
 
 export function useAuth() {
   const store = useAuthStore();
-  const { data, isLoading, isError } = useCurrentUser();
+  const { data, isLoading, isError, error } = useCurrentUser();
 
   useEffect(() => {
     if (isError) {
-      store.setAuthenticated(false);
-      store.setUser(null);
+      const status = (error as any)?.status || 0;
+      // Only logout on 401 Unauthorized — other errors are transient
+      if (status === 401) {
+        store.setAuthenticated(false);
+        store.setUser(null);
+      }
+      // For 403, 500, network errors: keep session, don't logout
     }
-  }, [isError, store]);
+  }, [isError, error, store]);
 
   return {
     user: store.user,