Convert web app to Electron desktop application

- Add Electron main process with developer tools support
- Create preload script for secure context bridge
- Configure electron-builder for packaging
- Update Vite config for Electron compatibility (base: './')
- Add environment variable support for API host configuration
- Fix i18n to use relative paths for Electron file protocol
- Restore multi-port backend architecture (8081-8085)
- Add enhanced backend startup script with port checking
- Update package.json with Electron dependencies and build scripts

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/i18n/i18n.ts

@@ -25,7 +25,7 @@ i18n
     
     // Backend options
     backend: {
-      loadPath: '/locales/{{lng}}/translation.json',
+      loadPath: './locales/{{lng}}/translation.json',
     },
     
     interpolation: {