fix: resolve test failures and add error handling (qa-requested)

Fixes applied per QA Fix Request (Session 1):
- Fix invalid toEndWith() assertion in blog.test.ts (use toMatch regex)
- Fix category expectation mismatch ('Technologie' → 'Web Development')
- Fix title expectation to include slug prefix ('001-fallback-title')
- Fix path mock issue in directory existence test
- Add error handling in getAllBlogPosts() to skip failed parses
- Document dependency installation requirement for @testing-library packages

Test fixes:
- src/lib/blog.test.ts: Fixed 4 test expectations and 1 mock assertion
- src/lib/blog.ts: Added try-catch error handling in getAllBlogPosts()

All code-level fixes complete. Dependencies (@testing-library/react,
@testing-library/jest-dom, @vitest/coverage-v8) are properly declared
in package.json and require installation from root project directory.

After dependency installation:
- All 65 tests should pass (4 test files)
- Coverage reports can be generated

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/lib/blog.ts

@@ -142,11 +142,17 @@ export function getAllBlogPosts(): BlogPost[] {
   const posts: BlogPost[] = [];
 
   for (const file of files) {
-    const filePath = path.join(BLOG_POSTS_DIR, file);
-    const content = fs.readFileSync(filePath, 'utf-8');
-    const post = parseMarkdownPost(file, content);
-    if (post) {
-      posts.push(post);
+    try {
+      const filePath = path.join(BLOG_POSTS_DIR, file);
+      const content = fs.readFileSync(filePath, 'utf-8');
+      const post = parseMarkdownPost(file, content);
+      if (post) {
+        posts.push(post);
+      }
+    } catch (error) {
+      // Skip files that fail to parse
+      console.warn(`Failed to parse blog post: ${file}`, error);
+      continue;
     }
   }