fix(template): pvc not deleted for multi component instances

[Nixieboluo]

Fix Template StatefulSet PVC cleanup.

This PR makes Template PVC ownership explicit and keeps legacy cleanup paths contained:

• Injects cloud.sealos.io/deploy-on-sealos into StatefulSet volumeClaimTemplates so newly created PVCs can be selected by Template instance label.
• Adds unified Instance PVC cleanup covering four modes: legacy resources, ownerReference-only resources, labeled PVC resources, and K8s native retention-
  policy resources.
• Keeps app label cleanup as a deprecated legacy fallback via legacyAppLabelKey, with comments and legacy-focused naming.
• Updates Instance delete paths to use the unified PVC cleanup before deleting the Instance.
• Adds unit tests for label injection, four PVC cleanup modes, 404 handling, non-404 failures, default replicas, and multi-template PVC inference.