Fix: Use Next.js server mode instead of static export

Static export (output: 'export') doesn't support server-side features
like API routes or server-side rendering. For Coolify deployment,
we need Next.js to run as a server.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

next.config.js

@@ -1,11 +1,8 @@
 /** @type {import('next').NextConfig} */
 const nextConfig = {
-  output: 'export',
-  distDir: 'dist',
   images: {
     unoptimized: true,
   },
-  trailingSlash: true,
 };
 
 module.exports = nextConfig;