feat(client): 首次登录改密守卫与错误文案(F35,F38)

- 登录响应支持 mustChangePassword 并强制跳转改密页
- 新增改密页面与全局路由守卫
- 完善 AUTH_002/SYS_429/VALID_00x 等错误提示

client/src/api/auth.ts

@@ -0,0 +1,19 @@
+import { apiRequestData } from "./http";
+import { getDeviceFingerprint } from "../auth/deviceFingerprint";
+import type { LoginResponse } from "./types";
+
+const JSON_HEADERS = {
+  "content-type": "application/json",
+};
+
+export async function changePassword(payload: { oldPassword: string; newPassword: string }) {
+  return apiRequestData<LoginResponse>("/api/auth/change-password", {
+    method: "POST",
+    headers: {
+      ...JSON_HEADERS,
+      "x-device-fingerprint": getDeviceFingerprint(),
+    },
+    body: JSON.stringify(payload),
+  });
+}
+