test: add comprehensive test suite for components, composables, and pages

Add 16 new test files covering:
- Composables: useBackend, useMeta, useDataJson
- Type classes: QueryResult, ResumeContent
- UI components: BadgeList, BadgeListCard
- Navbar components: LanguageSwitcher, ThemeSwitcher
- App components: AppNavbar, AppFooter
- VocalSynth components: Projects, Tools
- Pages: contact, resume, [...slug]

Tests focus on pure logic, interfaces, and component rendering where
possible, avoiding complex mocking of Nuxt auto-imported composables.

Total: 174 tests across 17 test files (including existing useApi tests).

app/pages/slug.test.ts

@@ -0,0 +1,126 @@
+import { describe, it, expect, vi } from 'vitest';
+import { mountSuspended } from '@nuxt/test-utils/runtime';
+import SlugPage from './[...slug].vue';
+
+// Mock useDataJson
+const mockPageContent = ref<{ title: string; description: string; meta?: { layout?: string } } | null>(null);
+const mockPageData = ref<Record<string, unknown> | null>(null);
+
+vi.mock('~/composables/useDataJson', () => ({
+  useDataJson: vi.fn((prefix: string) => {
+    if (prefix === 'page') {
+      return {
+        getPageContent: vi.fn(async () => mockPageContent),
+      };
+    }
+    if (prefix === 'page-data') {
+      return {
+        getJsonData: vi.fn(async () => mockPageData),
+      };
+    }
+    return {
+      getPageContent: vi.fn(async () => mockPageContent),
+      getJsonData: vi.fn(async () => mockPageData),
+    };
+  }),
+}));
+
+// Mock useMeta
+vi.mock('~/composables/useMeta', () => ({
+  useMeta: vi.fn(),
+}));
+
+describe('Slug Page (Catch-all)', () => {
+  describe('rendering', () => {
+    it('should render the page when content exists', async () => {
+      mockPageContent.value = {
+        title: 'Test Page',
+        description: 'A test page',
+      };
+
+      const wrapper = await mountSuspended(SlugPage);
+
+      expect(wrapper.exists()).toBe(true);
+    });
+
+    it('should show not found message when page is null', async () => {
+      mockPageContent.value = null;
+
+      const wrapper = await mountSuspended(SlugPage);
+
+      expect(wrapper.text()).toContain('Page not found');
+    });
+  });
+
+  describe('layout selection', () => {
+    it('should use default layout when no custom layout specified', async () => {
+      mockPageContent.value = {
+        title: 'Test Page',
+        description: 'A test page',
+      };
+
+      const wrapper = await mountSuspended(SlugPage);
+
+      expect(wrapper.exists()).toBe(true);
+    });
+
+    it('should use custom layout when specified in meta', async () => {
+      mockPageContent.value = {
+        title: 'Centered Page',
+        description: 'A centered page',
+        meta: { layout: 'centered' },
+      };
+
+      const wrapper = await mountSuspended(SlugPage);
+
+      expect(wrapper.exists()).toBe(true);
+    });
+  });
+
+  describe('page data injection', () => {
+    it('should provide pageData to child components', async () => {
+      mockPageContent.value = {
+        title: 'Vocal Synthesis',
+        description: 'Vocal synthesis projects',
+      };
+      mockPageData.value = {
+        projects: [{ title: 'Project 1' }],
+        tools: [{ name: 'Tool 1' }],
+      };
+
+      const wrapper = await mountSuspended(SlugPage);
+
+      // Page data should be provided for MDC components
+      expect(wrapper.exists()).toBe(true);
+    });
+  });
+
+  describe('content rendering', () => {
+    it('should render ContentRenderer when page exists', async () => {
+      mockPageContent.value = {
+        title: 'Test Content',
+        description: 'Test description',
+      };
+
+      const wrapper = await mountSuspended(SlugPage);
+
+      expect(wrapper.exists()).toBe(true);
+    });
+  });
+
+  describe('SEO meta', () => {
+    it('should call useMeta with page title and description', async () => {
+      const { useMeta } = await import('~/composables/useMeta');
+
+      mockPageContent.value = {
+        title: 'SEO Test Page',
+        description: 'Testing SEO metadata',
+      };
+
+      await mountSuspended(SlugPage);
+
+      // useMeta should have been called
+      expect(useMeta).toHaveBeenCalled();
+    });
+  });
+});