feat(cli): add experimental CRUD for sync entities (SyncOplogEntry, SyncDevice)

[cpcloud]

Summary

Add micasa db CRUD commands for sync-related entities:

• sync-oplog — list/get sync oplog entries
• sync-device — list/get/delete sync devices

These should be marked experimental (subject to change) since the sync system is still evolving.

Context

PR #934 adds micasa db CRUD for all user-facing entities. Sync entities were deferred because they're internal machinery, but CLI access is useful for debugging sync issues.

Scope

• Read-only for oplog (list, get) — oplog entries should not be manually created/edited
• CRUD for devices (list, get, delete) — deleting a device deregisters it from sync
• Experimental flag or help text warning

Follows from #920.

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