feat: 添加 Docker Compose 编排文件

- frontend 和 backend 两个服务，共享 camtalk-net 网络
- backend 通过 .env 注入 API Key，不对外暴露端口
- frontend 通过 Nginx 反代对外暴露 80 端口

docker-compose.yml

@@ -0,0 +1,30 @@
+services:
+  frontend:
+    build:
+      context: ./frontend
+      dockerfile: Dockerfile
+    container_name: camtalk-frontend
+    ports:
+      - "80:80"
+    depends_on:
+      - backend
+    networks:
+      - camtalk-net
+    restart: unless-stopped
+
+  backend:
+    build:
+      context: ./backend
+      dockerfile: Dockerfile
+    container_name: camtalk-backend
+    env_file:
+      - .env
+    environment:
+      - APP_ENV=production
+    networks:
+      - camtalk-net
+    restart: unless-stopped
+
+networks:
+  camtalk-net:
+    driver: bridge