refactor: 员工同步数据库配置改为环境变量

- 前端隐藏数据库连接配置输入
- 只保留"启用开关"和"表名"配置
- 数据库连接从 EMPLOYEE_SYNC_DB_URL 环境变量读取
- 显示数据源配置状态
- 保留默认值用于向后兼容

backend/app/services/employee_sync_service.py

@@ -23,8 +23,7 @@ logger = get_logger(__name__)
 class EmployeeSyncService:
     """员工同步服务"""
     
-    # 默认外部数据库连接配置（向后兼容）
-    DEFAULT_DB_URL = "mysql+aiomysql://neuron_new:NWxGM6CQoMLKyEszXhfuLBIIo1QbeK@120.77.144.233:29613/neuron_new?charset=utf8mb4"
+    # 默认外部数据库连接配置（向后兼容，从环境变量读取）
     DEFAULT_TABLE_NAME = "v_钉钉员工表"
     
     def __init__(self, db: AsyncSession, tenant_id: int = 1):
@@ -34,46 +33,43 @@ class EmployeeSyncService:
         self.table_name = self.DEFAULT_TABLE_NAME
         self._db_url = None
     
-    async def _get_config_from_db(self) -> tuple:
-        """从数据库获取员工同步配置"""
-        result = await self.db.execute(
-            text("""
-                SELECT config_key, config_value 
-                FROM tenant_configs 
-                WHERE tenant_id = :tenant_id AND config_group = 'employee_sync'
-            """),
-            {"tenant_id": self.tenant_id}
-        )
-        rows = result.fetchall()
-        
-        config = {}
-        for key, value in rows:
-            config[key] = value
-        
-        return config
+    async def _get_table_name_from_db(self) -> str:
+        """从数据库获取员工表名配置"""
+        try:
+            result = await self.db.execute(
+                text("""
+                    SELECT config_value 
+                    FROM tenant_configs 
+                    WHERE tenant_id = :tenant_id 
+                    AND config_group = 'employee_sync' 
+                    AND config_key = 'TABLE_NAME'
+                """),
+                {"tenant_id": self.tenant_id}
+            )
+            row = result.fetchone()
+            return row[0] if row else self.DEFAULT_TABLE_NAME
+        except Exception:
+            return self.DEFAULT_TABLE_NAME
     
-    async def _build_db_url(self) -> str:
-        """构建数据库连接URL"""
-        config = await self._get_config_from_db()
+    def _get_db_url_from_env(self) -> str:
+        """从环境变量获取数据库连接URL"""
+        import os
         
-        db_host = config.get('DB_HOST')
-        db_port = config.get('DB_PORT')
-        db_name = config.get('DB_NAME')
-        db_user = config.get('DB_USER')
-        db_password = config.get('DB_PASSWORD')
-        self.table_name = config.get('TABLE_NAME') or self.DEFAULT_TABLE_NAME
+        # 优先使用环境变量中的完整URL
+        db_url = os.environ.get('EMPLOYEE_SYNC_DB_URL', '')
         
-        # 如果配置完整，使用配置的URL
-        if all([db_host, db_port, db_name, db_user, db_password]):
-            return f"mysql+aiomysql://{db_user}:{db_password}@{db_host}:{db_port}/{db_name}?charset=utf8mb4"
+        if db_url:
+            return db_url
         
-        # 否则使用默认配置
-        logger.warning(f"租户 {self.tenant_id} 未配置员工同步数据库，使用默认配置")
-        return self.DEFAULT_DB_URL
+        # 向后兼容：如果没有配置环境变量，使用默认值
+        logger.warning("EMPLOYEE_SYNC_DB_URL 环境变量未配置，使用默认数据源")
+        return "mysql+aiomysql://neuron_new:NWxGM6CQoMLKyEszXhfuLBIIo1QbeK@120.77.144.233:29613/neuron_new?charset=utf8mb4"
         
     async def __aenter__(self):
         """异步上下文管理器入口"""
-        self._db_url = await self._build_db_url()
+        self._db_url = self._get_db_url_from_env()
+        self.table_name = await self._get_table_name_from_db()
+        
         self.external_engine = create_async_engine(
             self._db_url,
             echo=False,