test: 添加完整测试套件（52 个文件，326 个用例）

基于 Vitest 搭建测试基础设施，覆盖后端纯函数、API 路由、
前端 hooks、UI 组件和页面级集成测试。

src/app/profile/page.test.tsx

@@ -0,0 +1,98 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, waitFor } from "@testing-library/react";
+import React from "react";
+import { ToastContext, type ToastContextValue } from "@/hooks/useToast";
+
+vi.mock("next/navigation", () => ({
+  useRouter: () => ({
+    push: vi.fn(),
+    back: vi.fn(),
+  }),
+}));
+
+vi.mock("@/lib/userId", () => ({
+  getUserId: vi.fn().mockReturnValue("user-1"),
+  getCachedProfile: vi.fn().mockReturnValue({ id: "user-1", username: "testuser", avatar: "🐱" }),
+  setCachedProfile: vi.fn(),
+  setCachedPreferences: vi.fn(),
+  logout: vi.fn(),
+}));
+
+vi.mock("@/lib/avatars", () => ({
+  getAvatarBg: vi.fn().mockReturnValue("bg-amber-100"),
+  AVATARS: [
+    { emoji: "🐱", bg: "bg-amber-100" },
+    { emoji: "🐶", bg: "bg-orange-100" },
+  ],
+}));
+
+vi.mock("@/components/ProfileFavoritesCard", () => ({
+  default: () => <div data-testid="favorites-card" />,
+}));
+
+const mockFetch = vi.fn();
+vi.stubGlobal("fetch", mockFetch);
+
+import ProfilePage from "./page";
+
+const toastCtx: ToastContextValue = { show: vi.fn() };
+
+function renderPage() {
+  return render(
+    React.createElement(
+      ToastContext.Provider,
+      { value: toastCtx },
+      React.createElement(ProfilePage),
+    ),
+  );
+}
+
+beforeEach(() => {
+  vi.clearAllMocks();
+  mockFetch.mockResolvedValue({
+    ok: true,
+    json: () =>
+      Promise.resolve({
+        id: "user-1",
+        username: "testuser",
+        avatar: "🐱",
+        email: null,
+        achievements: {
+          totalDecisions: 5,
+          unanimousCount: 2,
+          roomsCreated: 3,
+          streak: 1,
+        },
+        records: [],
+        favorites: [],
+      }),
+  });
+});
+
+describe("ProfilePage", () => {
+  it("renders profile heading", () => {
+    renderPage();
+    expect(screen.getByText("个人中心")).toBeInTheDocument();
+  });
+
+  it("fetches user profile data with correct URL", async () => {
+    renderPage();
+    await waitFor(() => {
+      expect(mockFetch).toHaveBeenCalledWith(
+        "/api/user?id=user-1",
+      );
+    });
+  });
+
+  it("renders user info after data loads", async () => {
+    renderPage();
+    await waitFor(() => {
+      expect(screen.getByText("testuser")).toBeInTheDocument();
+    });
+  });
+
+  it("renders navigation element", () => {
+    renderPage();
+    expect(screen.getByRole("navigation")).toBeInTheDocument();
+  });
+});