feat: 侧边栏默认亮色主题，暗黑主题下跟随切换

frontend/src/__tests__/components/AppLayout.test.tsx

@@ -72,4 +72,36 @@ describe('AppLayout', () => {
     const header = container.querySelector('.ant-layout-header') as HTMLElement;
     expect(header.style.background).toBe('#141414');
   });
+
+  it('uses light menu theme in default mode', async () => {
+    const { useTheme } = await import('@/contexts/ThemeContext');
+    vi.mocked(useTheme).mockReturnValue({
+      effectiveThemeId: 'default',
+      themeId: 'default',
+      followSystem: false,
+      systemIsDark: false,
+      setThemeId: vi.fn(),
+      setFollowSystem: vi.fn(),
+    });
+
+    const { container } = renderWithRouter(<AppLayout />);
+    expect(container.querySelector('.ant-menu-light')).toBeInTheDocument();
+    expect(container.querySelector('.ant-menu-dark')).not.toBeInTheDocument();
+  });
+
+  it('uses dark menu theme in dark mode', async () => {
+    const { useTheme } = await import('@/contexts/ThemeContext');
+    vi.mocked(useTheme).mockReturnValue({
+      effectiveThemeId: 'dark',
+      themeId: 'dark',
+      followSystem: false,
+      systemIsDark: false,
+      setThemeId: vi.fn(),
+      setFollowSystem: vi.fn(),
+    });
+
+    const { container } = renderWithRouter(<AppLayout />);
+    expect(container.querySelector('.ant-menu-dark')).toBeInTheDocument();
+    expect(container.querySelector('.ant-menu-light')).not.toBeInTheDocument();
+  });
 });