Post-hardening C1: extract ClusterResourceApplyService from MigrationResource

[fmenesesg]

Summary

Wave C PR1: Move Kubernetes apply/revert/drift logic out of MigrationResource into a dedicated service.

Scope

• New service/cluster/ClusterResourceApplyService (apply, delete, drift)
• MigrationResource delegates K8s operations; keeps REST orchestration (audit, metrics, DevHub)
• Unit tests for apply strategy (serverSideApply vs Route createOr) and drift detection

Acceptance criteria

• No K8s YAML apply/delete/drift logic in MigrationResource
• ClusterResourceApplyServiceTest covers drift + apply paths
• mvn test passes

Wave C roadmap (follow-up PRs)

• C2: BackendEndpointResolver extraction from MigrationService
• C3: OpenApiSynthesisService extraction
• C4: Dead code removal + consolidationWarnings persistence