Watch delete failures do not trigger recovery sync

[ScottMorris]

Summary

Watch-initiated delete failures do not trigger a recovery sync, which can leave phone and watch alarm state diverged.

Current behaviour

• On wear:alarm:delete, failures are only logged.
• No emit_sync_needed(..., ForceSync) is sent on delete failure.

Expected behaviour

When a watch delete operation fails, the app should request a ForceSync so watch and phone state reconverge.

Impact

• Watch can keep showing alarms that failed to delete on phone.
• Divergence can persist until a manual sync or unrelated later event.

Evidence

• apps/threshold/src-tauri/src/lib.rs:238
• Save path does trigger recovery sync: apps/threshold/src-tauri/src/lib.rs:199

Suggested fix

Mirror the save failure path: emit SyncReason::ForceSync after delete failure.