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/Core/Models/Local/CanonicalModels.swift

@@ -69,6 +69,15 @@ final class SyncState {
     var gameChangeToken: Data?
     var leagueChangeToken: Data?
 
+    // Per-entity sync timestamps for partial progress
+    var lastStadiumSync: Date?
+    var lastTeamSync: Date?
+    var lastGameSync: Date?
+    var lastLeagueStructureSync: Date?
+    var lastTeamAliasSync: Date?
+    var lastStadiumAliasSync: Date?
+    var lastSportSync: Date?
+
     init() {}
 
     static func current(in context: ModelContext) -> SyncState {