Add Swahili (sw) Language Support

### Summary
This enhancement adds Swahili (Kiswahili) language support to DrawDB, expanding the application's accessibility to Swahili-speaking users across East Africa and beyond.

### Motivation
DrawDB currently supports 47 languages, making it accessible to users worldwide. Adding Swahili will:
- Extend support to over 200 million Swahili speakers globally
- Improve accessibility for users in Kenya, Tanzania, Uganda, and other East African countries
- Continue DrawDB's mission of being a truly international database design tool

### Proposed Implementation
The implementation follows the existing i18n pattern:

1. **Create locale file**: `src/i18n/locales/sw.js`
- Contains all 284+ translation keys
- Includes language metadata (name, native_name, code)
- Follows the same structure as existing locale files

2. **Update i18n configuration**: `src/i18n/i18n.js`
- Import Swahili locale
- Add to languages array
- Register in i18n resources

3. **Language metadata**:
- **Code**: `sw`
- **Name**: Swahili
- **Native Name**: Kiswahili
- **Direction**: LTR (Left-to-Right)

### Testing
- Language appears in the language selector
- UI elements display Swahili translations correctly
- Language preference persists across sessions
- Application builds without errors

### Related Files
- `src/i18n/locales/sw.js` (new)
- `src/i18n/i18n.js` (modified)

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**Note**: This follows the contribution guidelines outlined in CONTRIBUTING.md and maintains consistency with the existing codebase.enhancement

Start by comparing an existing locale file under src/i18n/locales/ with the requested structure, then inspect src/i18n/i18n.js for imports, language metadata, and resource registration. Add the Swahili locale and configuration entries, then verify the language selector, translated UI, preference persistence, and application build as described.

Written by the indexing model from the issue text.