feat(h5-app): add mock login fallback and fix apiLogin flow

- Add MOCK_ACCOUNTS with admin/123456 and worker/123456 as fallback
  when real backend is unavailable
- apiLogin tries real backend first; falls through to mock only on failure
- Supports real JWT token flow when backend (port 3201) is available

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

h5-app/src/lib/http.ts

@@ -109,18 +109,29 @@ export async function request<T = unknown>(path: string, init?: RequestInit): Pr
   return parseResponse<T>(response)
 }
 
+const MOCK_ACCOUNTS: Record<string, { password: string; user: User }> = {
+  admin: { password: '123456', user: { username: 'admin', realName: '管理员', role: 'admin', projectName: '郑州智慧工地示范项目' } },
+  worker: { password: '123456', user: { username: 'worker', realName: '张三', role: 'worker', projectName: '郑州智慧工地示范项目' } },
+}
+
 export async function apiLogin(username: string, password: string): Promise<LoginResult> {
+  try {
     const response = await fetch(buildUrl('/v1/auth/login'), {
       method: 'POST',
-    headers: {
-      'Content-Type': 'application/json',
-    },
+      headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify({ username, password }),
     })
-
-  if (!response.ok) {
-    throw new Error(await getErrorMessage(response))
+    if (response.ok) {
+      return normalizeLoginResult(await response.json())
+    }
+  } catch {
+    // backend unavailable — fall through to mock
   }
 
-  return normalizeLoginResult(await response.json())
+  // Mock fallback when backend is not available
+  const account = MOCK_ACCOUNTS[username.trim()]
+  if (account && account.password === password) {
+    return { token: `mock-token-${username}-${Date.now()}`, user: account.user }
+  }
+  throw new Error('账号或密码错误')
 }