fix: 修复员工同步功能开关保存失败的问题

当 feature_switches 表中没有默认记录时，set_feature_switch 函数
现在会使用预定义的默认值创建记录，而不是静默失败

backend/app/api/v1/system_settings.py

@@ -168,7 +168,26 @@ async def set_feature_switch(db: AsyncSession, tenant_id: int, feature_code: str
         )
         default_row = result.fetchone()
         
+        # 定义功能开关默认值映射
+        FEATURE_DEFAULTS = {
+            'employee_sync': ('员工同步', 'system', '从钉钉同步员工信息'),
+            'dingtalk_login': ('钉钉免密登录', 'system', '允许通过钉钉免密登录'),
+            'ai_practice': ('AI 对练', 'feature', 'AI 对练功能'),
+            'dual_practice': ('双人对练', 'feature', '双人对练功能'),
+        }
+        
         if default_row:
+            feature_name = default_row[0]
+            feature_group = default_row[1]
+            description = default_row[2]
+        elif feature_code in FEATURE_DEFAULTS:
+            feature_name, feature_group, description = FEATURE_DEFAULTS[feature_code]
+        else:
+            # 未知功能码，使用默认值
+            feature_name = feature_code
+            feature_group = 'system'
+            description = f'{feature_code} 功能开关'
+        
         # 插入租户级配置
         await db.execute(
             text("""
@@ -178,10 +197,10 @@ async def set_feature_switch(db: AsyncSession, tenant_id: int, feature_code: str
             {
                 "tenant_id": tenant_id,
                 "feature_code": feature_code,
-                    "feature_name": default_row[0],
-                    "feature_group": default_row[1],
+                "feature_name": feature_name,
+                "feature_group": feature_group,
                 "is_enabled": 1 if is_enabled else 0,
-                    "description": default_row[2]
+                "description": description
             }
         )