feat(auth): add email/password login restricted to @craze.de accounts

- src/lib/auth.ts: signIn/signOut/getStoredSession via Supabase Auth REST API
- src/components/LoginPage.tsx: login form with domain validation UI
- src/components/TopBar.tsx: show logged-in user email + sign out button
- src/App.tsx: gate entire app behind auth — shows LoginPage if no session

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

src/App.tsx

@@ -8,8 +8,21 @@ import { MatrixView } from './components/MatrixView';
 import { UploadReload } from './components/UploadReload';
 import { EditPanel } from './components/EditPanel';
 import { getAllSyncedRows, saveRowToSupabase } from './lib/supabase';
+import { getStoredSession, signOut, type AuthSession } from './lib/auth';
+import { LoginPage } from './components/LoginPage';
 
 export default function App() {
+  const [session, setSession] = useState<AuthSession | null>(() => getStoredSession());
+
+  const handleSignOut = () => {
+    signOut();
+    setSession(null);
+  };
+
+  if (!session) {
+    return <LoginPage onLogin={() => setSession(getStoredSession())} />;
+  }
+
   const [appState, setAppState] = useState<AppState>({
     headers: [],
     data: [],
@@ -192,11 +205,13 @@ export default function App() {
 
   return (
     <div className="h-screen bg-slate-900 text-slate-200 flex flex-col font-sans overflow-hidden">
-      <TopBar 
-        stats={stats} 
-        onExport={handleExport} 
-        hasData={appState.data.length > 0} 
+      <TopBar
+        stats={stats}
+        onExport={handleExport}
+        hasData={appState.data.length > 0}
         hasUnsavedChanges={appState.hasUnsavedChanges}
+        userEmail={session.user.email}
+        onSignOut={handleSignOut}
       />
       <div className="flex flex-1 overflow-hidden">
         <Sidebar activeModule={activeModule} setActiveModule={setActiveModule} />