feat(ops): 后端添加指标阈值管理API

- 新增GetMetricThresholds和UpdateMetricThresholds接口
- 支持配置SLA、延迟P99、TTFT P99、请求错误率、上游错误率阈值
- 添加参数验证逻辑
- 提供默认阈值配置

backend/internal/service/ops_settings.go

@@ -463,3 +463,94 @@ func (s *OpsService) UpdateOpsAdvancedSettings(ctx context.Context, cfg *OpsAdva
 	_ = json.Unmarshal(raw, updated)
 	return updated, nil
 }
+
+// =========================
+// Metric thresholds
+// =========================
+
+const SettingKeyOpsMetricThresholds = "ops_metric_thresholds"
+
+func defaultOpsMetricThresholds() *OpsMetricThresholds {
+	slaMin := 99.5
+	latencyMax := 2000.0
+	ttftMax := 500.0
+	reqErrMax := 5.0
+	upstreamErrMax := 5.0
+	return &OpsMetricThresholds{
+		SLAPercentMin:               &slaMin,
+		LatencyP99MsMax:             &latencyMax,
+		TTFTp99MsMax:                &ttftMax,
+		RequestErrorRatePercentMax:  &reqErrMax,
+		UpstreamErrorRatePercentMax: &upstreamErrMax,
+	}
+}
+
+func (s *OpsService) GetMetricThresholds(ctx context.Context) (*OpsMetricThresholds, error) {
+	defaultCfg := defaultOpsMetricThresholds()
+	if s == nil || s.settingRepo == nil {
+		return defaultCfg, nil
+	}
+	if ctx == nil {
+		ctx = context.Background()
+	}
+
+	raw, err := s.settingRepo.GetValue(ctx, SettingKeyOpsMetricThresholds)
+	if err != nil {
+		if errors.Is(err, ErrSettingNotFound) {
+			if b, mErr := json.Marshal(defaultCfg); mErr == nil {
+				_ = s.settingRepo.Set(ctx, SettingKeyOpsMetricThresholds, string(b))
+			}
+			return defaultCfg, nil
+		}
+		return nil, err
+	}
+
+	cfg := &OpsMetricThresholds{}
+	if err := json.Unmarshal([]byte(raw), cfg); err != nil {
+		return defaultCfg, nil
+	}
+
+	return cfg, nil
+}
+
+func (s *OpsService) UpdateMetricThresholds(ctx context.Context, cfg *OpsMetricThresholds) (*OpsMetricThresholds, error) {
+	if s == nil || s.settingRepo == nil {
+		return nil, errors.New("setting repository not initialized")
+	}
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	if cfg == nil {
+		return nil, errors.New("invalid config")
+	}
+
+	// Validate thresholds
+	if cfg.SLAPercentMin != nil && (*cfg.SLAPercentMin < 0 || *cfg.SLAPercentMin > 100) {
+		return nil, errors.New("sla_percent_min must be between 0 and 100")
+	}
+	if cfg.LatencyP99MsMax != nil && *cfg.LatencyP99MsMax < 0 {
+		return nil, errors.New("latency_p99_ms_max must be >= 0")
+	}
+	if cfg.TTFTp99MsMax != nil && *cfg.TTFTp99MsMax < 0 {
+		return nil, errors.New("ttft_p99_ms_max must be >= 0")
+	}
+	if cfg.RequestErrorRatePercentMax != nil && (*cfg.RequestErrorRatePercentMax < 0 || *cfg.RequestErrorRatePercentMax > 100) {
+		return nil, errors.New("request_error_rate_percent_max must be between 0 and 100")
+	}
+	if cfg.UpstreamErrorRatePercentMax != nil && (*cfg.UpstreamErrorRatePercentMax < 0 || *cfg.UpstreamErrorRatePercentMax > 100) {
+		return nil, errors.New("upstream_error_rate_percent_max must be between 0 and 100")
+	}
+
+	raw, err := json.Marshal(cfg)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.settingRepo.Set(ctx, SettingKeyOpsMetricThresholds, string(raw)); err != nil {
+		return nil, err
+	}
+
+	updated := &OpsMetricThresholds{}
+	_ = json.Unmarshal(raw, updated)
+	return updated, nil
+}
+

backend/internal/service/ops_settings_models.go

@@ -61,11 +61,20 @@ type OpsAlertSilencingSettings struct {
 	Entries []OpsAlertSilenceEntry `json:"entries,omitempty"`
 }
 
+type OpsMetricThresholds struct {
+	SLAPercentMin               *float64 `json:"sla_percent_min,omitempty"`                // SLA低于此值变红
+	LatencyP99MsMax             *float64 `json:"latency_p99_ms_max,omitempty"`             // 延迟P99高于此值变红
+	TTFTp99MsMax                *float64 `json:"ttft_p99_ms_max,omitempty"`                // TTFT P99高于此值变红
+	RequestErrorRatePercentMax  *float64 `json:"request_error_rate_percent_max,omitempty"` // 请求错误率高于此值变红
+	UpstreamErrorRatePercentMax *float64 `json:"upstream_error_rate_percent_max,omitempty"` // 上游错误率高于此值变红
+}
+
 type OpsAlertRuntimeSettings struct {
 	EvaluationIntervalSeconds int `json:"evaluation_interval_seconds"`
 
 	DistributedLock OpsDistributedLockSettings `json:"distributed_lock"`
 	Silencing       OpsAlertSilencingSettings  `json:"silencing"`
+	Thresholds      OpsMetricThresholds        `json:"thresholds"` // 指标阈值配置
 }
 
 // OpsAdvancedSettings stores advanced ops configuration (data retention, aggregation).