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

jest.config.json

@@ -6,6 +6,7 @@
     "<rootDir>/services/**/__tests__/**/*.test.ts",
     "<rootDir>/utils/**/__tests__/**/*.test.ts",
     "<rootDir>/types/**/__tests__/**/*.test.ts",
+    "<rootDir>/components/**/__tests__/**/*.test.tsx",
     "<rootDir>/tests/**/*.test.ts",
     "<rootDir>/tests/**/*.test.js"
   ],