fix: clean up deleting restore PVCs

[weicao]

Summary

• handle a deleting restore PVC before validating its source Backup
• keep the target PVC finalizer while owned populate Jobs or the helper PVC still exist
• release the target finalizer only after a fresh reconcile confirms the dependents are absent
• preserve the existing non-deletion cleanup behavior for bound PVC completion

Tests

• go test ./controllers/dataprotection -run '^TestSyncPVCDeletion' -count=1
• go test ./controllers/dataprotection -run '^Test(SyncPVCDeletion|CompleteBoundPVC|ProvisionOnly)' -count=1
• KUBEBUILDER_ASSETS='<envtest 1.26.1 assets>' go test ./controllers/dataprotection -count=1
• git diff HEAD^..HEAD --check

The PR remains draft until the patch image is validated against the focused restore cleanup scenario.

[apecloud-bot]

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[apecloud-bot]

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