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/CanonicalSyncService.swift

@@ -42,12 +42,13 @@ actor CanonicalSyncService {
         let gamesUpdated: Int
         let leagueStructuresUpdated: Int
         let teamAliasesUpdated: Int
+        let stadiumAliasesUpdated: Int
         let skippedIncompatible: Int
         let skippedOlder: Int
         let duration: TimeInterval
 
         var totalUpdated: Int {
-            stadiumsUpdated + teamsUpdated + gamesUpdated + leagueStructuresUpdated + teamAliasesUpdated
+            stadiumsUpdated + teamsUpdated + gamesUpdated + leagueStructuresUpdated + teamAliasesUpdated + stadiumAliasesUpdated
         }
 
         var isEmpty: Bool { totalUpdated == 0 }
@@ -81,7 +82,7 @@ actor CanonicalSyncService {
         guard syncState.syncEnabled else {
             return SyncResult(
                 stadiumsUpdated: 0, teamsUpdated: 0, gamesUpdated: 0,
-                leagueStructuresUpdated: 0, teamAliasesUpdated: 0,
+                leagueStructuresUpdated: 0, teamAliasesUpdated: 0, stadiumAliasesUpdated: 0,
                 skippedIncompatible: 0, skippedOlder: 0,
                 duration: 0
             )
@@ -101,6 +102,7 @@ actor CanonicalSyncService {
         var totalGames = 0
         var totalLeagueStructures = 0
         var totalTeamAliases = 0
+        var totalStadiumAliases = 0
         var totalSkippedIncompatible = 0
         var totalSkippedOlder = 0
 
@@ -138,13 +140,21 @@ actor CanonicalSyncService {
             totalSkippedIncompatible += skipIncompat4
             totalSkippedOlder += skipOlder4
 
-            let (games, skipIncompat5, skipOlder5) = try await syncGames(
+            let (stadiumAliases, skipIncompat5, skipOlder5) = try await syncStadiumAliases(
+                context: context,
+                since: syncState.lastSuccessfulSync
+            )
+            totalStadiumAliases = stadiumAliases
+            totalSkippedIncompatible += skipIncompat5
+            totalSkippedOlder += skipOlder5
+
+            let (games, skipIncompat6, skipOlder6) = try await syncGames(
                 context: context,
                 since: syncState.lastSuccessfulSync
             )
             totalGames = games
-            totalSkippedIncompatible += skipIncompat5
-            totalSkippedOlder += skipOlder5
+            totalSkippedIncompatible += skipIncompat6
+            totalSkippedOlder += skipOlder6
 
             // Mark sync successful
             syncState.syncInProgress = false
@@ -176,6 +186,7 @@ actor CanonicalSyncService {
             gamesUpdated: totalGames,
             leagueStructuresUpdated: totalLeagueStructures,
             teamAliasesUpdated: totalTeamAliases,
+            stadiumAliasesUpdated: totalStadiumAliases,
             skippedIncompatible: totalSkippedIncompatible,
             skippedOlder: totalSkippedOlder,
             duration: Date().timeIntervalSince(startTime)
@@ -346,6 +357,30 @@ actor CanonicalSyncService {
         return (updated, skippedIncompatible, skippedOlder)
     }
 
+    @MainActor
+    private func syncStadiumAliases(
+        context: ModelContext,
+        since lastSync: Date?
+    ) async throws -> (updated: Int, skippedIncompatible: Int, skippedOlder: Int) {
+        let remoteAliases = try await cloudKitService.fetchStadiumAliasChanges(since: lastSync)
+
+        var updated = 0
+        var skippedIncompatible = 0
+        var skippedOlder = 0
+
+        for remoteAlias in remoteAliases {
+            let result = try mergeStadiumAlias(remoteAlias, context: context)
+
+            switch result {
+            case .applied: updated += 1
+            case .skippedIncompatible: skippedIncompatible += 1
+            case .skippedOlder: skippedOlder += 1
+            }
+        }
+
+        return (updated, skippedIncompatible, skippedOlder)
+    }
+
     // MARK: - Merge Logic
 
     private enum MergeResult {
@@ -631,4 +666,41 @@ actor CanonicalSyncService {
             return .applied
         }
     }
+
+    @MainActor
+    private func mergeStadiumAlias(
+        _ remote: StadiumAlias,
+        context: ModelContext
+    ) throws -> MergeResult {
+        // Schema version check
+        guard remote.schemaVersion <= SchemaVersion.current else {
+            return .skippedIncompatible
+        }
+
+        let remoteAliasName = remote.aliasName
+        let descriptor = FetchDescriptor<StadiumAlias>(
+            predicate: #Predicate { $0.aliasName == remoteAliasName }
+        )
+        let existing = try context.fetch(descriptor).first
+
+        if let existing = existing {
+            // lastModified check
+            guard remote.lastModified > existing.lastModified else {
+                return .skippedOlder
+            }
+
+            // Update all fields (no user fields on StadiumAlias)
+            existing.stadiumCanonicalId = remote.stadiumCanonicalId
+            existing.validFrom = remote.validFrom
+            existing.validUntil = remote.validUntil
+            existing.schemaVersion = remote.schemaVersion
+            existing.lastModified = remote.lastModified
+
+            return .applied
+        } else {
+            // Insert new
+            context.insert(remote)
+            return .applied
+        }
+    }
 }