feat(ui): F1+F2 — component primitives + rebuilt app shell

F1: shadcn-style primitive set in components/ui (Button, Card, Badge, Input,
Switch, Separator, Skeleton, Tooltip, DropdownMenu, Dialog, Sheet, Tabs, Table,
Toast+useToast, ThemeToggle, PageHeader/StatCard/EmptyState) on Radix + cva.

F2: Layout rebuilt on the new system — sidebar with primary nav (lucide icons)
+ favorites/saved-searches/mailbox/smart-folder sections, sticky topbar with
search, sync status, theme toggle, digest toggle, and an account dropdown. All
prior behavior preserved (auth, sync, collapse/section persistence, "/" search
focus). App wrapped in ToastProvider + TooltipProvider. Build green.

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

frontend/src/main.jsx

@@ -9,13 +9,16 @@ import Unsubscribe from './pages/Unsubscribe.jsx';
 import FolderView from './pages/FolderView.jsx';
 import SearchResults from './pages/SearchResults.jsx';
 import Layout from './components/Layout.jsx';
+import { ToastProvider, TooltipProvider } from './components/ui';
 import './index.css';
 import './styles.css';
 
 ReactDOM.createRoot(document.getElementById('root')).render(
   <React.StrictMode>
-    <BrowserRouter>
-      <Routes>
+    <ToastProvider>
+      <TooltipProvider delayDuration={200}>
+        <BrowserRouter>
+          <Routes>
         {/* Public landing page */}
         <Route path="/" element={<Landing />} />
 
@@ -29,8 +32,10 @@ ReactDOM.createRoot(document.getElementById('root')).render(
           <Route path="search" element={<SearchResults />} />
         </Route>
 
-        <Route path="*" element={<Navigate to="/" replace />} />
-      </Routes>
-    </BrowserRouter>
+            <Route path="*" element={<Navigate to="/" replace />} />
+          </Routes>
+        </BrowserRouter>
+      </TooltipProvider>
+    </ToastProvider>
   </React.StrictMode>
 );