feat(group): 添加 MCP XML 注入开关

- Group 新增 mcp_xml_inject 字段，控制 Antigravity 平台的 MCP XML 协议注入
- 默认启用，可在分组设置中关闭
- 修复 GetByKeyForAuth 遗漏查询 mcp_xml_inject 字段导致认证缓存值始终为 false 的问题

backend/ent/runtime/runtime.go

@@ -284,6 +284,10 @@ func init() {
 	groupDescModelRoutingEnabled := groupFields[18].Descriptor()
 	// group.DefaultModelRoutingEnabled holds the default value on creation for the model_routing_enabled field.
 	group.DefaultModelRoutingEnabled = groupDescModelRoutingEnabled.Default.(bool)
+	// groupDescMcpXMLInject is the schema descriptor for mcp_xml_inject field.
+	groupDescMcpXMLInject := groupFields[19].Descriptor()
+	// group.DefaultMcpXMLInject holds the default value on creation for the mcp_xml_inject field.
+	group.DefaultMcpXMLInject = groupDescMcpXMLInject.Default.(bool)
 	promocodeFields := schema.PromoCode{}.Fields()
 	_ = promocodeFields
 	// promocodeDescCode is the schema descriptor for code field.