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/components/ui/sonner.tsx

@@ -1,5 +1,5 @@
 import { useTheme } from "next-themes"
-import { Toaster as Sonner, ToasterProps } from "sonner"
+import { Toaster as Sonner, type ToasterProps } from "sonner"
 
 const Toaster = ({ ...props }: ToasterProps) => {
   const { theme = "system" } = useTheme()