[feat] front: 페이지 골격(Login/List/Chat) 추가

- 라우팅 대상 빈 화면 페이지 3종
- named + default export 동시 제공

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

front/src/pages/ChatPage.tsx

@@ -0,0 +1,5 @@
+export function ChatPage() {
+  return <main className="min-h-svh" />
+}
+
+export default ChatPage

front/src/pages/ListPage.tsx

@@ -0,0 +1,5 @@
+export function ListPage() {
+  return <main className="min-h-svh" />
+}
+
+export default ListPage

front/src/pages/LoginPage.tsx

@@ -0,0 +1,5 @@
+export function LoginPage() {
+  return <main className="min-h-svh" />
+}
+
+export default LoginPage