fix: real K8s replicas in list API, full Helm values in modify YAML editor

- Add Replicas field to entity.Instance
- Add EnrichReplicas to InstanceService (batch K8s deployment query)
- convertInstanceResponse uses instance.Replicas instead of hardcoded 0
- ModifyModal: load full Helm values from values-diff API (Current deployed)
- Remove stale loadValuesDiff, use single useEffect for all data loading
- Fix YAML lineWidth:0 for no line wrapping

backend/internal/domain/entity/instance.go

@@ -53,6 +53,7 @@ type Instance struct {
 	Revision      int // Helm Release Revision
 	CreatedAt     time.Time
 	UpdatedAt     time.Time
+	Replicas      int // Running K8s replicas (enriched, not persisted)
 }
 
 // NewInstance 创建新实例