feat(ops): 添加分组和账号级别监控指标

- 后端新增 GetAccountAvailability 方法获取账号可用性数据
- 添加分组可用率和限流率计算辅助函数
- 前端支持分组和账号级别的监控指标类型
- 优化警报规则指标选择器,按类别分组显示

backend/internal/service/ops_service.go

@@ -28,6 +28,9 @@ type OpsService struct {
 
 	accountRepo AccountRepository
 
+	// getAccountAvailability is a unit-test hook for overriding account availability lookup.
+	getAccountAvailability func(ctx context.Context, platformFilter string, groupIDFilter *int64) (*OpsAccountAvailability, error)
+
 	concurrencyService        *ConcurrencyService
 	gatewayService            *GatewayService
 	openAIGatewayService      *OpenAIGatewayService