feat(auth): Google ile Giriş + landing/login + çalışan çıkış + admin rolü

- server/auth.mjs: ID token'ı oauth2.googleapis.com/tokeninfo ile doğrula (ek bağımlılık yok), HMAC imzalı app token, ADMIN_EMAILS ile admin
- POST /api/auth/google, GET /api/auth/google/config, GET /api/auth/me
- LoginPage: GIS butonlu landing/giriş; giriş yapılmadan uygulama açılmaz
- Header çıkış butonu artık çalışıyor; kullanıcı adı/avatar Google'dan
- AI Model Ayarları sekmesi sadece admin'e görünür
- Env: GOOGLE_CLIENT_ID + ADMIN_EMAILS (Coolify'dan)

src/App.jsx

@@ -26,9 +26,10 @@ import { AnalyticsDashboard } from './components/tools/AnalyticsDashboard';
 import { ApiWebhooks } from './components/tools/ApiWebhooks';
 import { PwaSettings } from './components/tools/PwaSettings';
 import { AiModelSettings } from './components/tools/AiModelSettings';
+import { LoginPage } from './components/LoginPage';
 
 const MainContent = () => {
-  const { activeTab } = useApp();
+  const { activeTab, isAdmin } = useApp();
 
   return (
     <main className="max-w-[1600px] mx-auto px-4 pb-12">
@@ -58,7 +59,7 @@ const MainContent = () => {
       {activeTab === 'analitik_dashboard' && <AnalyticsDashboard />}
       {activeTab === 'api_webhooks' && <ApiWebhooks />}
       {activeTab === 'pwa_settings' && <PwaSettings />}
-      {activeTab === 'ai_ayarlari' && <AiModelSettings />}
+      {activeTab === 'ai_ayarlari' && isAdmin && <AiModelSettings />}
 
       {/* Global Modals */}
       <DetailedSearchModal />
@@ -69,15 +70,33 @@ const MainContent = () => {
   );
 };
 
+const Gate = () => {
+  const { authReady, isAuthenticated, handleLogin } = useApp();
+
+  if (!authReady) {
+    return (
+      <div className="min-h-screen bg-[#0f172a] flex items-center justify-center text-white/70">
+        Yükleniyor…
+      </div>
+    );
+  }
+  if (!isAuthenticated) {
+    return <LoginPage onLogin={handleLogin} />;
+  }
+  return (
+    <div className="min-h-screen bg-[#f3f5f8] text-slate-800 flex flex-col font-['Inter',sans-serif]">
+      <Header />
+      <LiveStatsBar />
+      <TopNavigation />
+      <MainContent />
+    </div>
+  );
+};
+
 export default function App() {
   return (
     <AppProvider>
-      <div className="min-h-screen bg-[#f3f5f8] text-slate-800 flex flex-col font-['Inter',sans-serif]">
-        <Header />
-        <LiveStatsBar />
-        <TopNavigation />
-        <MainContent />
-      </div>
+      <Gate />
     </AppProvider>
   );
 }