build: add Docker Compose setup for Dokploy deployment

- Multi-stage Dockerfile for Go backend (golang:1.25-alpine -> alpine:3)
- Multi-stage Dockerfile for Next.js frontend (bun:1 -> node:22-alpine)
- docker-compose.yml with backend + frontend services, health checks
- Next.js standalone output + API rewrites to proxy /api/* to backend
- .dockerignore files for both services
- .env.example documenting required environment variables

frontend/next.config.ts

@@ -1,7 +1,13 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  /* config options here */
+  output: "standalone",
+  rewrites: async () => [
+    {
+      source: "/api/:path*",
+      destination: `${process.env.API_URL || "http://localhost:8080"}/:path*`,
+    },
+  ],
 };
 
 export default nextConfig;