feat: Add per-workspace backup status tracking with annotations

[tolusha]

What does this PR do?

Enhance the backup cronjob controller to track backup status individually for each workspace using annotations. This allows more granular control over when backups are triggered based on each workspace's specific backup history rather than a global timestamp.

• Add handleBackupJobStatus to update DevWorkspace annotations when backup jobs complete or fail
• Modify wasStoppedSinceLastBackup to check workspace-specific annotations first, falling back to global time
• Include DevWorkspace name label on backup jobs for easier association

Assisted-by: Claude

What issues does this PR fix or reference?

#1549

Is it tested? How?

TODO

PR Checklist

• E2E tests pass (when PR is ready, comment /test v8-devworkspace-operator-e2e, v8-che-happy-path to trigger)
  • v8-devworkspace-operator-e2e: DevWorkspace e2e test
  • v8-che-happy-path: Happy path for verification integration with Che

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[openshift-ci]

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This pull-request has been approved by: tolusha
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