完成后端配置，用于部署

backend/database.py

@@ -0,0 +1,22 @@
+from sqlalchemy import create_engine, MetaData, Table
+from .config import settings
+
+class Database:
+    def __init__(self):
+        self.engine = create_engine(settings.DATABASE_URL, pool_pre_ping=True)
+        self.metadata = MetaData()
+        self.tasks = None
+        self.queue = None
+        self.chunks = None
+        self._reflect_tables()
+
+    def _reflect_tables(self):
+        try:
+            # 自动从数据库加载表结构
+            self.tasks = Table('crawl_tasks', self.metadata, autoload_with=self.engine)
+            self.queue = Table('crawl_queue', self.metadata, autoload_with=self.engine)
+            self.chunks = Table('knowledge_chunks', self.metadata, autoload_with=self.engine)
+        except Exception as e:
+            print(f"❌ 数据库表加载失败: {e}")
+
+db_instance = Database()