feat：简单添加管理员后台功能

client/src/lib/adminAuth.ts

@@ -0,0 +1,17 @@
+const TOKEN_KEY = 'whale_town_admin_token';
+
+export function getToken(): string | null {
+  return localStorage.getItem(TOKEN_KEY);
+}
+
+export function setToken(token: string): void {
+  localStorage.setItem(TOKEN_KEY, token);
+}
+
+export function clearAuth(): void {
+  localStorage.removeItem(TOKEN_KEY);
+}
+
+export function isAuthed(): boolean {
+  return Boolean(getToken());
+}