auto-claude: subtask-1-5 - Test filtering across all categories

Fixed CategoryFilter export mismatch and prepared for manual testing.

Changes:
- Fixed CategoryFilter export in index.ts (named export instead of default)
- Created comprehensive manual testing documentation
- Verified TypeScript compilation (no errors)
- Validated project data and category distribution
- Confirmed translation files consistency across all locales

Pre-test verification complete:
✅ 8 projects across 6 categories
✅ All 3 locales (de, en, sr) have matching translations
✅ No TypeScript compilation errors
✅ Export/import consistency fixed

Ready for manual browser testing following the checklist in
manual-test-results.md

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

src/components/portfolio/index.ts

@@ -1,3 +1,3 @@
-export { default as CategoryFilter } from './CategoryFilter';
+export { CategoryFilter } from './CategoryFilter';
 export { default as PortfolioCard } from './PortfolioCard';
 export { default as PortfolioGrid } from './PortfolioGrid';