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

docker-compose.yml

@@ -0,0 +1,33 @@
+services:
+  backend:
+    build:
+      context: ./backend
+    expose:
+      - "8080"
+    env_file:
+      - .env
+    environment:
+      - PORT=8080
+    healthcheck:
+      test: ["CMD", "wget", "--spider", "-q", "http://localhost:8080/health"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 5s
+
+  frontend:
+    build:
+      context: ./frontend
+    ports:
+      - "3000:3000"
+    depends_on:
+      backend:
+        condition: service_healthy
+    env_file:
+      - .env
+    healthcheck:
+      test: ["CMD", "wget", "--spider", "-q", "http://localhost:3000"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 10s