Implement Offline-First Sync

Background: Native [platform] app, [SwiftUI+Combine / Compose]. Users
need to [read / create / edit] this data while offline and have it sync
when back online: [describe the data and operations]. Backend: [chosen].

Use case: Design an offline-first sync system so the app is fully usable
with no connection and reconciles cleanly when it returns.

Implementation details:
- Local store as the source of truth the UI reads from; network sync
  happens in the background
- An outbox/queue for offline writes, with retry and ordering guarantees
- Conflict resolution strategy (last-write-wins, server-wins, merge, or
  per-field)—recommend one for my data and explain the tradeoff
- Detecting connectivity changes and triggering sync (NWPathMonitor /
  ConnectivityManager + WorkManager)
- Marking records pending/syncing/synced/failed and surfacing that in UI
- Idempotency so retried writes don't duplicate

Layer & dependencies: Sync logic lives in the data layer; the UI only
sees local data and a sync-status indicator.

Deliverable: An offline-first architecture, the write-queue and
sync-trigger design, the conflict-resolution rules with their tradeoffs,
the record state model, and the failure/retry behavior.