2.0: CloudKit private-database sync replaces KV snapshot sync

Foundation for 2.1 family sharing (CKShare needs these models + container).
SwiftData cannot share across Apple IDs today, so 2.0 ships true multi-device
sync for the same account instead:

- Models made CloudKit-compatible: dropped @Attribute(.unique) on all 5,
  inline defaults on every attribute, WeekPlan.slots stored as optional
  relationship (name preserved → lightweight migration) with non-optional
  slotList facade; ~73 call sites renamed.
- Container: cloudKitDatabase .automatic, falling back to the local-only
  store when CloudKit is unavailable; failures recorded to Crashlytics.
- Entitlements: iCloud CloudKit service (container already existed);
  remote-notification background mode for push-driven sync.
- Legacy KV snapshot sync (ICloudSyncService) stays inert when CloudKit is
  active — kept only for 1.x devices.
- DeduplicationService collapses cross-device duplicates deterministically on
  launch (settings singleton, default tags with tagId remapping, same-week
  plans).
- Note: AppSettings.isPremium now syncs across same-Apple-ID devices; StoreKit
  (PremiumSyncService + Transaction.updates) remains the source of truth and
  reconciles on every launch/foreground.

All 21 unit tests pass, including ICloudSyncPremiumIsolationTests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BkanrydYtrme8wipTzWssG

MealMood/Models/MealSlot.swift

@@ -1,11 +1,12 @@
 import Foundation
 import SwiftData
 
+// CloudKit-compatible (2.0): no unique constraints, inline defaults everywhere.
 @Model
 final class MealSlot {
-    @Attribute(.unique) var id: UUID
-    var dayOfWeek: Int // 0=Monday, 6=Sunday
-    var mealType: String // "lunch", "dinner"
+    var id: UUID = UUID()
+    var dayOfWeek: Int = 0 // 0=Monday, 6=Sunday
+    var mealType: String = MealType.dinner.rawValue
     var dishId: UUID?
     var calendarEventId: String?
     var isRuleOverridden: Bool = false