Offline write queue (notes + mark-as-read)

[fboucher]

Parent PRD

#110

Depends on

#124 (offline read mode must be in place)

Summary

All write operations (create note, edit note, mark post as read) made while offline are queued via IsPendingSync = true and replayed in order when connectivity is restored. Soft-delete support included.

Write operations to queue

• Create note (new Note with IsPendingSync = true)
• Edit note (updated Note with IsPendingSync = true, DateModified = UtcNow)
• Mark post as read (Post with is_read = true, IsPendingSync = true, DateModified = UtcNow)
• Delete note (soft-delete: IsDeleted = true, IsPendingSync = true)

Queue behaviour

• Writes are accepted immediately and stored in SQLite
• Order of writes preserved (by DateModified)
• User sees their changes instantly in the UI (optimistic local state)

Acceptance Criteria

• Create note while offline → stored locally with IsPendingSync = true
• Edit note while offline → stored locally with updated DateModified
• Mark-as-read while offline → stored locally with IsPendingSync = true
• Delete note while offline → soft-deleted locally (IsDeleted = true, IsPendingSync = true)
• UI reflects changes immediately without waiting for sync
• Pending items visible via ILocalDataService.GetPendingSyncPostsAsync/NotesAsync()

Stories from PRD

User stories 4, 5, 6, 18