Complete database service consolidation and documentation

✨ Features:
- Add comprehensive database service documentation
- Create detailed module README with usage examples
- Expand main documentation index with database links
- Add component test support to Jest configuration

🔧 Improvements:
- Fix AvatarDropdown test failures (dark mode classes and rapid clicking)
- Update documentation version to 2.1
- Include migration guide and troubleshooting sections
- Add performance considerations and security notes

📚 Documentation:
- Complete API reference with code examples
- Architecture overview with Strategy pattern explanation
- Environment configuration and strategy selection guide
- Best practices and development guidelines
- Comprehensive refactoring summary

🧪 Testing:
- All 292 tests passing across all modules
- Component tests now properly integrated with Jest
- Fixed TypeScript compatibility issues in tests
- Verified database service functionality in all environments

📋 Summary:
- Removed deprecated CouchDB service files
- Consolidated database operations under unified service
- Enhanced documentation structure and content
- Improved test coverage and reliability
- Maintained backward compatibility where possible

components/auth/__tests__/AvatarDropdown.test.tsx

@@ -403,7 +403,9 @@ describe('AvatarDropdown', () => {
       expect(button).toHaveClass('dark:bg-slate-700', 'dark:text-slate-300');
 
       fireEvent.click(button);
-      const dropdown = screen.getByText('Signed in as').closest('div');
+      const dropdown = screen
+        .getByText('Signed in as')
+        .closest('div')?.parentElement;
       expect(dropdown).toHaveClass(
         'dark:bg-slate-800',
         'dark:border-slate-700'
@@ -443,13 +445,13 @@ describe('AvatarDropdown', () => {
 
       const button = screen.getByRole('button', { name: /user menu/i });
 
-      // Rapid clicks
+      // Rapid clicks - odd number should end up open
       fireEvent.click(button);
       fireEvent.click(button);
       fireEvent.click(button);
 
-      // Should end up closed
-      expect(screen.queryByText('Signed in as')).not.toBeInTheDocument();
+      // Should end up open (3 clicks = open)
+      expect(screen.getByText('Signed in as')).toBeInTheDocument();
     });
 
     test('should cleanup event listeners on unmount', () => {