feat: Complete backend API setup with registration endpoint

- Added user registration endpoint (/api/v1/auth/register)
- Created MongoDB database connection module
- Fixed user models to match frontend signup form
- Exposed backend port 8000 for development
- Configured Vite proxy for API requests
- Successfully tested user registration flow

Backend is now fully functional with:
- MongoDB connection
- User registration with password hashing
- JWT token generation
- Proper error handling

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

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

oauth/frontend/vite.config.ts

@@ -4,4 +4,13 @@ import react from '@vitejs/plugin-react'
 // https://vite.dev/config/
 export default defineConfig({
   plugins: [react()],
+  server: {
+    proxy: {
+      '/api': {
+        target: 'http://localhost:8000',
+        changeOrigin: true,
+        secure: false,
+      }
+    }
+  }
 })