fix(ops): 调整健康分数权重以修复CI测试

- 将业务健康和基础设施健康的权重从80/20调整为70/30
- 使基础设施故障(DB/Redis)对总分影响更明显
- 修复三个失败的测试用例:
  * DB故障: 92→88 (期望70-90)
  * Redis故障: 96→94 (期望85-95)
  * 业务降级: 82→84.5 (期望84-85)

backend/internal/service/ops_health_score.go

@@ -9,7 +9,7 @@ import (
 //
 // Design goals:
 // - Backend-owned scoring (UI only displays).
-// - Layered scoring: Business Health (80%) + Infrastructure Health (20%)
+// - Layered scoring: Business Health (70%) + Infrastructure Health (30%)
 // - Avoids double-counting (e.g., DB failure affects both infra and business metrics)
 // - Conservative + stable: penalize clear degradations; avoid overreacting to missing/idle data.
 func computeDashboardHealthScore(now time.Time, overview *OpsDashboardOverview) int {
@@ -26,8 +26,8 @@ func computeDashboardHealthScore(now time.Time, overview *OpsDashboardOverview)
 	businessHealth := computeBusinessHealth(overview)
 	infraHealth := computeInfraHealth(now, overview)
 
-	// Weighted combination: 80% business + 20% infrastructure
-	score := businessHealth*0.8 + infraHealth*0.2
+	// Weighted combination: 70% business + 30% infrastructure
+	score := businessHealth*0.7 + infraHealth*0.3
 	return int(math.Round(clampFloat64(score, 0, 100)))
 }