Add StadiumAlias CloudKit sync and offline-first data architecture

- Add CKStadiumAlias model for CloudKit record mapping
- Add fetchStadiumAliases/fetchStadiumAliasChanges to CloudKitService
- Add syncStadiumAliases to CanonicalSyncService for delta sync
- Add subscribeToStadiumAliasUpdates for push notifications
- Update cloudkit_import.py with --stadium-aliases-only option

Data Architecture Updates:
- Remove obsolete provider files (CanonicalDataProvider, CloudKitDataProvider, StubDataProvider)
- AppDataProvider now reads exclusively from SwiftData
- Add background CloudKit sync on app startup (non-blocking)
- Document data architecture in CLAUDE.md

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

SportsTime/Core/Services/CloudKitService.swift

@@ -228,6 +228,24 @@ actor CloudKitService {
         }
     }
 
+    func fetchStadiumAliases(for stadiumCanonicalId: String? = nil) async throws -> [StadiumAlias] {
+        let predicate: NSPredicate
+        if let stadiumId = stadiumCanonicalId {
+            predicate = NSPredicate(format: "stadiumCanonicalId == %@", stadiumId)
+        } else {
+            predicate = NSPredicate(value: true)
+        }
+
+        let query = CKQuery(recordType: CKRecordType.stadiumAlias, predicate: predicate)
+
+        let (results, _) = try await publicDatabase.records(matching: query)
+
+        return results.compactMap { result in
+            guard case .success(let record) = result.1 else { return nil }
+            return CKStadiumAlias(record: record).toModel()
+        }
+    }
+
     // MARK: - Delta Sync (Date-Based for Public Database)
 
     /// Fetch league structure records modified after the given date
@@ -270,6 +288,26 @@ actor CloudKitService {
         }
     }
 
+    /// Fetch stadium alias records modified after the given date
+    func fetchStadiumAliasChanges(since lastSync: Date?) async throws -> [StadiumAlias] {
+        let predicate: NSPredicate
+        if let lastSync = lastSync {
+            predicate = NSPredicate(format: "lastModified > %@", lastSync as NSDate)
+        } else {
+            predicate = NSPredicate(value: true)
+        }
+
+        let query = CKQuery(recordType: CKRecordType.stadiumAlias, predicate: predicate)
+        query.sortDescriptors = [NSSortDescriptor(key: CKStadiumAlias.lastModifiedKey, ascending: true)]
+
+        let (results, _) = try await publicDatabase.records(matching: query)
+
+        return results.compactMap { result in
+            guard case .success(let record) = result.1 else { return nil }
+            return CKStadiumAlias(record: record).toModel()
+        }
+    }
+
     // MARK: - Sync Status
 
     func checkAccountStatus() async -> CKAccountStatus {
@@ -327,10 +365,26 @@ actor CloudKitService {
         try await publicDatabase.save(subscription)
     }
 
+    func subscribeToStadiumAliasUpdates() async throws {
+        let subscription = CKQuerySubscription(
+            recordType: CKRecordType.stadiumAlias,
+            predicate: NSPredicate(value: true),
+            subscriptionID: "stadium-alias-updates",
+            options: [.firesOnRecordCreation, .firesOnRecordUpdate]
+        )
+
+        let notification = CKSubscription.NotificationInfo()
+        notification.shouldSendContentAvailable = true
+        subscription.notificationInfo = notification
+
+        try await publicDatabase.save(subscription)
+    }
+
     /// Subscribe to all canonical data updates
     func subscribeToAllUpdates() async throws {
         try await subscribeToScheduleUpdates()
         try await subscribeToLeagueStructureUpdates()
         try await subscribeToTeamAliasUpdates()
+        try await subscribeToStadiumAliasUpdates()
     }
 }