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

backend/Dockerfile

@@ -0,0 +1,15 @@
+# Build
+FROM golang:1.25-alpine AS builder
+WORKDIR /app
+COPY go.mod ./
+RUN go mod download
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux go build -o server ./cmd/server
+
+# Run
+FROM alpine:3
+RUN apk --no-cache add ca-certificates
+WORKDIR /app
+COPY --from=builder /app/server .
+EXPOSE 8080
+CMD ["./server"]