feat: 添加后端环境配置和 Docker Compose 示例文件

- 添加 backend/.env.example 环境变量模板
- 添加 backend/docker-compose.example.yml Docker 配置示例
- 更新 frontend/.env.local 配置注释

backend/docker-compose.example.yml

@@ -0,0 +1,54 @@
+version: '3.8'
+
+services:
+  backend:
+    image: registry.cn-hangzhou.aliyuncs.com/photography/backend:latest
+    container_name: photography_backend
+    restart: unless-stopped
+    network_mode: host  # 使用主机网络连接现有的PostgreSQL和Redis
+    environment:
+      # 数据库配置 (连接现有的PostgreSQL)
+      DB_HOST: ${DB_HOST:-localhost}
+      DB_PORT: ${DB_PORT:-5432}
+      DB_NAME: ${DB_NAME:-photography}
+      DB_USER: ${DB_USER:-postgres}
+      DB_PASSWORD: ${DB_PASSWORD:-your_password}
+      DB_SSLMODE: ${DB_SSLMODE:-disable}
+      
+      # Redis配置 (连接现有的Redis)
+      REDIS_HOST: ${REDIS_HOST:-localhost}
+      REDIS_PORT: ${REDIS_PORT:-6379}
+      REDIS_PASSWORD: ${REDIS_PASSWORD:-}
+      REDIS_DB: ${REDIS_DB:-0}
+      
+      # JWT配置
+      JWT_SECRET: ${JWT_SECRET:-your_jwt_secret_key}
+      JWT_EXPIRE: ${JWT_EXPIRE:-24h}
+      
+      # 服务配置
+      APP_ENV: ${APP_ENV:-production}
+      APP_PORT: ${APP_PORT:-8080}
+      APP_HOST: ${APP_HOST:-0.0.0.0}
+      
+      # 文件上传配置
+      UPLOAD_DIR: ${UPLOAD_DIR:-/app/uploads}
+      MAX_FILE_SIZE: ${MAX_FILE_SIZE:-10485760}  # 10MB
+      
+      # CORS配置
+      CORS_ORIGINS: ${CORS_ORIGINS:-https://photography.iriver.top,https://admin.photography.iriver.top}
+      
+      # 日志配置
+      LOG_LEVEL: ${LOG_LEVEL:-info}
+      
+    volumes:
+      # 文件上传存储
+      - /home/gitea/photography/uploads:/app/uploads
+      # 日志存储  
+      - /home/gitea/photography/logs:/app/logs
+      
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:8080/health"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 40s