feat(sync): add pagination, cancellation, and network restoration

- CloudKit pagination: fetchAllRecords() handles >400 record batches
  with cursor-based pagination (400 records per page)
- Cancellation support: SyncCancellationToken protocol enables graceful
  sync termination when background tasks expire
- Per-entity progress: SyncState now tracks timestamps per entity type
  so interrupted syncs resume where they left off
- NetworkMonitor: NWPathMonitor integration triggers sync on network
  restoration with 2.5s debounce to handle WiFi↔cellular flapping
- wasCancelled flag in SyncResult distinguishes partial from full syncs

This addresses critical data sync issues:
- CloudKit queries were limited to ~400 records but bundled data has ~5000 games
- Background tasks could be killed mid-sync without saving progress
- App had no awareness of network state changes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

SportsTime/SportsTimeApp.swift

@@ -152,13 +152,19 @@ struct BootstrappedContentView: View {
             await StoreManager.shared.loadProducts()
             await StoreManager.shared.updateEntitlements()
 
-            // 6. App is now usable
+            // 6. Start network monitoring and wire up sync callback
+            NetworkMonitor.shared.onSyncNeeded = {
+                await BackgroundSyncManager.shared.triggerSyncFromNetworkRestoration()
+            }
+            NetworkMonitor.shared.startMonitoring()
+
+            // 7. App is now usable
             isBootstrapping = false
 
-            // 7. Schedule background tasks for future syncs
+            // 8. Schedule background tasks for future syncs
             BackgroundSyncManager.shared.scheduleAllTasks()
 
-            // 8. Background: Try to refresh from CloudKit (non-blocking)
+            // 9. Background: Try to refresh from CloudKit (non-blocking)
             Task.detached(priority: .background) {
                 await self.performBackgroundSync(context: context)
                 await MainActor.run {