Add basePath /bodenfeuchte for reverse proxy deployment

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

next.config.ts

@@ -1,7 +1,7 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  /* config options here */
+  basePath: '/bodenfeuchte',
 };
 
 export default nextConfig;