fix: 限制数据库连接池大小避免超出 PostgreSQL max_connections

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docker-compose.yml

@@ -53,6 +53,8 @@ services:
       - REDIS_URL=redis://redis:6379
       - REDIS_PASSWORD=${REDIS_PASSWORD:-redis123}
       - ENCRYPTION_KEY=${ENCRYPTION_KEY:-wxcz-aigc-default-encryption-key}
+      - DB_POOL_SIZE=3
+      - DB_MAX_OVERFLOW=2
       - APP_HOST=0.0.0.0
       - APP_PORT=8010
       - DEBUG=${DEBUG:-false}