feat(mlflow): add KOTS snapshot/backup configuration for stateful services

[kriscoleman]

Parent epic: #166
Integration branch: feat/mlflow-enterprise-patterns

Add KOTS snapshot configuration for PostgreSQL and MinIO PVCs with restore documentation.

Scope

• Add backup configuration to release/kots-app.yaml: backup.volumes for PostgreSQL and MinIO PVCs
• Add snapshot-related preflight collector to release/kots-preflight.yaml (Velero/snapshot provider check)
• Create applications/mlflow/docs/backup-restore.md documenting:
  • How KOTS snapshots work with CloudnativePG and MinIO Tenant PVCs
  • Full backup procedure
  • Restore procedure with operator ordering considerations
  • Verification steps post-restore

Files touched

• applications/mlflow/release/kots-app.yaml (add backup config)
• applications/mlflow/release/kots-preflight.yaml (add snapshot check)
• applications/mlflow/docs/backup-restore.md (new file)

PR target

Branch PRs to feat/mlflow-enterprise-patterns (not main).