fix: use absolute path for DATABASE_URL in Docker

docker-compose.yml

@@ -12,7 +12,7 @@ services:
       # 持久化数据库文件
       - student-data:/app/data
     environment:
-      - DATABASE_URL=file:./data/student.db
+      - DATABASE_URL=file:/app/data/student.db
       - NODE_ENV=production
     restart: unless-stopped
     healthcheck: