refactor: improve search tests, stories, and docs

- Add unit tests for all 4 search providers (38 tests)
- Remove unused SearchCategory types (orders, workshops, volunteers)
- Refactor Storybook stories with reusable SearchModalShell/ResultsList
- Add Loading and PagesOnly story variants
- Update docs to reflect current implementation

Author: Starefossen

docs/ENHANCED_SEARCH_IMPLEMENTATION.md

@@ -123,11 +123,11 @@ Ready to implement when needed (documented in README):
 
 ## Testing & Quality
 
-- ✅ **ESLint**: No linting errors
-- ✅ **TypeScript**: Full type safety
-- ✅ **Storybook**: Stories updated (builds successfully)
-- ✅ **Code Review**: All feedback addressed
-- ✅ **Security**: CodeQL scan - 0 vulnerabilities found
+- **Unit Tests**: All 4 search providers have comprehensive test suites (`__tests__/lib/search/`)
+- **Storybook**: Stories cover empty, results, loading, no-results, error, and single-category states
+- **ESLint**: No linting errors
+- **TypeScript**: Full type safety
+- **Knip**: No unused exports
 
 ## Files Changed
 
@@ -141,7 +141,11 @@ Ready to implement when needed (documented in README):
 - `src/lib/search/providers/index.ts` - Provider exports
 - `src/lib/search/hooks/useUnifiedSearch.ts` - Unified search hook
 - `src/lib/search/index.ts` - Module exports
-- `src/lib/search/README.md` - Comprehensive documentation
+- `src/lib/search/README.md` - Architecture documentation
+- `__tests__/lib/search/AdminPagesSearchProvider.test.ts` - Admin pages tests
+- `__tests__/lib/search/ProposalsSearchProvider.test.ts` - Proposals tests
+- `__tests__/lib/search/SponsorsSearchProvider.test.ts` - Sponsors tests
+- `__tests__/lib/search/SpeakersSearchProvider.test.ts` - Speakers tests
 
 ### Modified