feat: add protected login workspace

src/app/page.tsx

@@ -271,6 +271,11 @@ export default function Home() {
     }
   }
 
+  async function handleLogout() {
+    await fetch('/api/auth/logout', { method: 'POST', credentials: 'include' });
+    window.location.href = '/login';
+  }
+
   return (
     <div className="flex h-screen text-white">
       <Sidebar
@@ -319,6 +324,12 @@ export default function Home() {
                   </a>
                 </>
               )}
+              <button
+                onClick={handleLogout}
+                className="chip chip-neutral hover:border-violet-300/40 hover:text-white transition-colors"
+              >
+                退出
+              </button>
               <span className={provider === 'gpt' ? 'chip chip-live' : provider === '?' ? 'chip chip-neutral' : 'chip chip-mock'}>
                 <span className={`w-1.5 h-1.5 rounded-full ${provider === 'gpt' ? 'bg-emerald-400' : provider === '?' ? 'bg-white/40' : 'bg-amber-400'}`} />
                 {provider === 'gpt' ? 'GPT · gpt-image-2' : provider === 'mock' ? 'Mock · 占位图' : provider === '?' ? '待连接' : provider}