fix: dismiss paywall and sync premium state after successful purchase

- Add purchaseSucceeded flag to PurchaseViewModel, set on purchase success
- PaywallView observes the flag and dismisses itself automatically
- ProfileTab.syncSubscription() writes PurchaseService.currentPlan back
  to UserProfile.subscriptionRaw via SwiftData on sheet dismiss

tabatago-swift/TabataGo/Views/Paywall/PaywallView.swift

@@ -112,6 +112,9 @@ struct PaywallView: View {
             }
         }
         .task { await vm.loadOfferings() }
+        .onChange(of: vm.purchaseSucceeded) { _, succeeded in
+            if succeeded { dismiss() }
+        }
         .onAppear { AnalyticsService.shared.paywallViewed(source: "paywall_sheet") }
         .alert("Error", isPresented: $vm.showError) {
             Button("OK") {}

tabatago-swift/TabataGo/Views/Tabs/ProfileTab.swift

@@ -8,6 +8,7 @@ struct ProfileTab: View {
     @State private var showingPaywall = false
     @Environment(\.modelContext) private var context
     @StateObject private var purchaseVM = PurchaseViewModel()
+    private let purchaseService = PurchaseService.shared
 
     private var profile: UserProfile? { profiles.first }
 
@@ -101,11 +102,19 @@ struct ProfileTab: View {
             }
             .navigationTitle("Profile")
             .navigationBarTitleDisplayMode(.large)
-            .sheet(isPresented: $showingPaywall) {
+            .sheet(isPresented: $showingPaywall, onDismiss: syncSubscription) {
                 PaywallView()
             }
         }
     }
+
+    private func syncSubscription() {
+        guard let profile else { return }
+        let newPlan = purchaseService.currentPlan
+        guard profile.subscription != newPlan else { return }
+        profile.subscriptionRaw = newPlan.rawValue
+        try? context.save()
+    }
 }
 
 struct ProfileRow: View {