HDDS-15165. Recon: Add admin REST APIs to trigger, monitor, and cancel SCM DB snapshot sync.

[devmadhuu]

What changes were proposed in this pull request?

This change adds Recon admin REST APIs to explicitly manage full SCM DB snapshot syncs as a follow-up to #10074.
The new APIs are exposed under TriggerDBSyncEndpoint:

  - POST /api/v1/triggerdbsync/scm/snapshot triggers an async full SCM DB snapshot download and refresh.
  - GET /api/v1/triggerdbsync/scm/snapshot/status returns current status, phase, start time, finish time, duration, cancellation eligibility, and last error.
  - POST /api/v1/triggerdbsync/scm/snapshot/cancel cancels the operation while checkpoint download is still in progress.

The implementation keeps full SCM snapshot recovery as an explicit admin action instead of coupling it to periodic SCM container sync. It tracks snapshot sync lifecycle state in ReconStorageContainerManagerFacade, prevents concurrent SCM DB sync operations, allows cancellation only before DB initialization starts, and cleans up failed or cancelled checkpoint directories.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-15165

How was this patch tested?

Tests were added for the new trigger/status/cancel endpoint behavior in TestTriggerDBSyncEndpoint.