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/widgets/knowledge_item_card.dart

@@ -2,12 +2,17 @@ import 'package:flutter/material.dart';
 import 'package:lucide_icons/lucide_icons.dart';
 import 'package:go_router/go_router.dart';
 
+import '../data/local/database.dart';
 import '../data/models/knowledge_item.dart';
+import 'pending_sync_badge.dart';
 
 class KnowledgeItemCard extends StatelessWidget {
   final KnowledgeItem item;
   const KnowledgeItemCard({super.key, required this.item});
 
+  String get _pendingDomain =>
+      item.noteType == 'task' ? kSyncDomainTasks : kSyncDomainNotes;
+
   IconData get _icon => switch (item.noteType) {
         'person' => LucideIcons.user,
         'place' => LucideIcons.mapPin,
@@ -52,10 +57,17 @@ class KnowledgeItemCard extends StatelessWidget {
   Widget build(BuildContext context) {
     return ListTile(
       leading: Icon(_icon, color: _statusColor(context)),
-      title: Text(
-        item.title.isEmpty ? '(untitled)' : item.title,
-        maxLines: 1,
-        overflow: TextOverflow.ellipsis,
+      title: Row(
+        children: [
+          Flexible(
+            child: Text(
+              item.title.isEmpty ? '(untitled)' : item.title,
+              maxLines: 1,
+              overflow: TextOverflow.ellipsis,
+            ),
+          ),
+          PendingSyncBadge(domain: _pendingDomain, id: item.id),
+        ],
       ),
       subtitle: _subtitle != null
           ? Text(
@@ -100,6 +112,7 @@ class KnowledgeItemCard extends StatelessWidget {
                           ?.copyWith(fontWeight: FontWeight.w600),
                     ),
                   ),
+                  PendingSyncBadge(domain: _pendingDomain, id: item.id),
                 ],
               ),
               if (_subtitle != null) ...[