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/screens/projects/projects_screen.dart

@@ -3,8 +3,10 @@ import 'package:lucide_icons/lucide_icons.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
+import '../../data/local/database.dart';
 import '../../data/models/project.dart';
 import '../../providers/projects_provider.dart';
+import '../../widgets/pending_sync_badge.dart';
 
 class ProjectsScreen extends ConsumerWidget {
   const ProjectsScreen({super.key});
@@ -50,7 +52,12 @@ class _ProjectCard extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return ListTile(
-      title: Text(project.title),
+      title: Row(
+        children: [
+          Flexible(child: Text(project.title)),
+          PendingSyncBadge(domain: kSyncDomainProjects, id: project.id),
+        ],
+      ),
       subtitle: Column(
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [