feat(offline): tier 2 phase 4 — per-row pending-sync indicators

A small cloud-upload glyph appears next to any row whose id has a
queued offline write (offline-created temp ids and pending edits both
count). Tooltip reads "Pending sync — will save when online". Renders
nothing during normal online operation so the list stays clean.

- DB: `watchPendingIds(domain)` streams the union of target_id and
  temp_id across the queue, scoped per domain.
- Per-domain Riverpod stream providers for notes / tasks / projects.
- New `PendingSyncBadge` widget — used by KnowledgeItemCard (both
  list and grid variants), `_ProjectCard`, and `_TaskRow` in the
  project workspace.

flutter analyze clean; 21 tests pass. Closes #147 — all four phases
of Tier 2 offline mode are in place.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/providers/api_client_provider.dart

@@ -173,3 +173,20 @@ final writeQueueDepthProvider = StreamProvider<int>((ref) {
 final writeQueueFailuresProvider = StreamProvider<QueueFailure>((ref) {
   return ref.watch(writeQueueProvider).failures;
 });
+
+/// Per-domain set of ids with a queued write (target_id ∪ temp_id). Phase 4
+/// — used by `PendingSyncBadge` in list views to mark rows that are still
+/// in flight.
+final pendingNoteIdsProvider = StreamProvider<Set<int>>((ref) {
+  return ref.watch(fabledDatabaseProvider).watchPendingIds(kSyncDomainNotes);
+});
+
+final pendingTaskIdsProvider = StreamProvider<Set<int>>((ref) {
+  return ref.watch(fabledDatabaseProvider).watchPendingIds(kSyncDomainTasks);
+});
+
+final pendingProjectIdsProvider = StreamProvider<Set<int>>((ref) {
+  return ref
+      .watch(fabledDatabaseProvider)
+      .watchPendingIds(kSyncDomainProjects);
+});