feat: complete Phase 3 — advanced features for Casera web app

Adds sharing (residence share codes, join, user management, .casera file
export/import), subscription status with feature comparison, notification
preferences with bell icon, profile settings (edit info, change password,
theme picker, delete account), onboarding wizard with create/join paths,
enhanced dashboard with stats cards, Recharts completion chart, recent
activity feed, and task report PDF download.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/query/query-client.ts

@@ -0,0 +1,26 @@
+import { QueryClient } from '@tanstack/react-query';
+
+export function makeQueryClient() {
+  return new QueryClient({
+    defaultOptions: {
+      queries: {
+        staleTime: 3_600_000, // 1 hour (matches DataManager cache timeout)
+        retry: 1,
+        refetchOnWindowFocus: true,
+      },
+      mutations: {
+        retry: 0,
+      },
+    },
+  });
+}
+
+let browserQueryClient: QueryClient | undefined;
+
+export function getQueryClient() {
+  // Server: always make a new query client
+  if (typeof window === 'undefined') return makeQueryClient();
+  // Browser: use a singleton
+  if (!browserQueryClient) browserQueryClient = makeQueryClient();
+  return browserQueryClient;
+}

src/lib/query/query-provider.tsx

@@ -0,0 +1,16 @@
+"use client";
+
+import { QueryClientProvider } from '@tanstack/react-query';
+import { ReactQueryDevtools } from '@tanstack/react-query-devtools';
+import { getQueryClient } from './query-client';
+
+export function QueryProvider({ children }: { children: React.ReactNode }) {
+  const queryClient = getQueryClient();
+
+  return (
+    <QueryClientProvider client={queryClient}>
+      {children}
+      <ReactQueryDevtools initialIsOpen={false} />
+    </QueryClientProvider>
+  );
+}