Align restore reconcile tests with backup phase validation

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TestRestoreReconcile still had cases using defaultBackup() in ReadyToStart, which now fails restore validation before the intended code path executes. This update applies the review suggestion by setting backup phase explicitly to Completed only in cases meant to proceed past validation.

• Review-comment scope only
  • Updated only the test fixtures called out by the review thread in pkg/controller/restore_controller_test.go.
• Behavior-preserving test intent
  • Cases that should exercise restore execution/failure paths now explicitly use a completed backup.
• Applied pattern

  // before
  defaultBackup().StorageLocation("default").Result()
  
  // after
  defaultBackup().StorageLocation("default").Phase(velerov1api.BackupPhaseCompleted).Result()

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• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file (make new-changelog) or comment /kind changelog-not-required on this PR.
• Updated the corresponding documentation in site/content/docs/main.

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