feat(frontend): add routing skeleton with workspace chat and login pages

src/pages/WorkspacePage.tsx

@@ -0,0 +1,8 @@
+export default function WorkspacePage() {
+  return (
+    <section>
+      <h2>工作台</h2>
+      <p>这里会展示 Guild/Channel 概览与会话入口。</p>
+    </section>
+  )
+}