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/composables/useMeta.test.ts

@@ -0,0 +1,101 @@
+import { describe, it, expect } from 'vitest';
+import type { MetaImageOptions, MetaOptions } from './useMeta';
+
+describe('useMeta', () => {
+  describe('MetaOptions interface', () => {
+    it('should accept required title and description', () => {
+      const options: MetaOptions = {
+        title: 'Test Page',
+        description: 'Test description',
+      };
+
+      expect(options.title).toBe('Test Page');
+      expect(options.description).toBe('Test description');
+      expect(options.image).toBeUndefined();
+    });
+
+    it('should accept optional image property', () => {
+      const options: MetaOptions = {
+        title: 'Test Page',
+        description: 'Test description',
+        image: {
+          url: 'https://example.com/image.jpg',
+          alt: 'Alt text',
+        },
+      };
+
+      expect(options.image).toBeDefined();
+      expect(options.image?.url).toBe('https://example.com/image.jpg');
+      expect(options.image?.alt).toBe('Alt text');
+    });
+  });
+
+  describe('MetaImageOptions interface', () => {
+    it('should require url and alt properties', () => {
+      const imageOptions: MetaImageOptions = {
+        url: 'https://example.com/image.png',
+        alt: 'Image description',
+      };
+
+      expect(imageOptions.url).toBe('https://example.com/image.png');
+      expect(imageOptions.alt).toBe('Image description');
+    });
+  });
+
+  describe('title suffix logic', () => {
+    const titleSuffix = ' – Lucien Cartier-Tilet';
+
+    it('should append suffix to title', () => {
+      const title = 'My Page';
+      const fullTitle = title + titleSuffix;
+
+      expect(fullTitle).toBe('My Page – Lucien Cartier-Tilet');
+    });
+
+    it('should handle empty title', () => {
+      const title = '';
+      const fullTitle = title + titleSuffix;
+
+      expect(fullTitle).toBe(' – Lucien Cartier-Tilet');
+    });
+  });
+
+  describe('twitter card type logic', () => {
+    it('should use summary_large_image when image is provided', () => {
+      const image: MetaImageOptions = { url: 'test.jpg', alt: 'Test' };
+      const cardType = image ? 'summary_large_image' : 'summary';
+
+      expect(cardType).toBe('summary_large_image');
+    });
+
+    it('should use summary when no image is provided', () => {
+      const image: MetaImageOptions | undefined = undefined;
+      const cardType = image ? 'summary_large_image' : 'summary';
+
+      expect(cardType).toBe('summary');
+    });
+  });
+
+  describe('optional chaining for image properties', () => {
+    it('should return url when image is provided', () => {
+      const options: MetaOptions = {
+        title: 'Test',
+        description: 'Test',
+        image: { url: 'https://example.com/og.jpg', alt: 'OG Image' },
+      };
+
+      expect(options.image?.url).toBe('https://example.com/og.jpg');
+      expect(options.image?.alt).toBe('OG Image');
+    });
+
+    it('should return undefined when image is not provided', () => {
+      const options: MetaOptions = {
+        title: 'Test',
+        description: 'Test',
+      };
+
+      expect(options.image?.url).toBeUndefined();
+      expect(options.image?.alt).toBeUndefined();
+    });
+  });
+});