feat(sync): add CloudKit sync for dynamic sports

- Add CKSport model to parse CloudKit Sport records
- Add fetchSportsForSync() to CloudKitService for delta fetching
- Add syncSports() and mergeSport() to CanonicalSyncService
- Update DataProvider with dynamicSports support and allSports computed property
- Update MockAppDataProvider with matching dynamic sports support
- Add comprehensive documentation for adding new sports

The app can now sync sport definitions from CloudKit, enabling new sports
to be added without app updates. Sports are fetched, merged into SwiftData,
and exposed via AppDataProvider.allSports alongside built-in Sport enum cases.

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

SportsTime/Core/Services/CloudKitService.swift

@@ -418,6 +418,27 @@ actor CloudKitService {
         }
     }
 
+    // MARK: - Sport Sync
+
+    /// Fetch sports for sync operations
+    /// - Parameter lastSync: If nil, fetches all sports. If provided, fetches only sports modified since that date.
+    func fetchSportsForSync(since lastSync: Date?) async throws -> [CanonicalSport] {
+        let predicate: NSPredicate
+        if let lastSync = lastSync {
+            predicate = NSPredicate(format: "modificationDate >= %@", lastSync as NSDate)
+        } else {
+            predicate = NSPredicate(value: true)
+        }
+        let query = CKQuery(recordType: CKRecordType.sport, predicate: predicate)
+
+        let (results, _) = try await publicDatabase.records(matching: query)
+
+        return results.compactMap { result -> CanonicalSport? in
+            guard case .success(let record) = result.1 else { return nil }
+            return CKSport(record: record).toCanonical()
+        }
+    }
+
     // MARK: - Sync Status
 
     func checkAccountStatus() async -> CKAccountStatus {