Add complete web interface with Next.js frontend

- Initialize Next.js 14 app with TypeScript and Tailwind CSS
- Create authentication flows (login, register, OAuth)
- Build dashboard with overview statistics
- Implement mail accounts management (list, add, edit, delete)
- Add auto-detect and test connection features
- Create responsive layout with sidebar navigation
- Configure Docker deployment for frontend
- Update docker-compose.new.yml with frontend service
- Add comprehensive web interface documentation

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/next.config.ts

@@ -2,6 +2,8 @@ import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
   /* config options here */
+  output: 'standalone',
+  reactStrictMode: true,
 };
 
 export default nextConfig;