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/Dockerfile

@@ -0,0 +1,28 @@
+# Dependencies
+FROM oven/bun:1 AS deps
+WORKDIR /app
+COPY package.json bun.lock ./
+RUN bun install --frozen-lockfile
+
+# Build
+FROM oven/bun:1 AS builder
+WORKDIR /app
+COPY --from=deps /app/node_modules ./node_modules
+COPY . .
+ENV API_URL=http://backend:8080
+RUN mkdir -p public
+RUN bun run build
+
+# Run
+FROM node:22-alpine AS runner
+WORKDIR /app
+ENV NODE_ENV=production
+ENV HOSTNAME=0.0.0.0
+ENV PORT=3000
+
+COPY --from=builder /app/.next/standalone ./
+COPY --from=builder /app/.next/static ./.next/static
+COPY --from=builder /app/public ./public
+
+EXPOSE 3000
+CMD ["node", "server.js"]