Add notification preferences UI and subscription verification on launch

- Add NotificationPreferencesScreen (Android) and NotificationPreferencesView (iOS)
- Add NotificationPreferencesViewModel for shared business logic
- Wire up notification preferences from ProfileScreen on both platforms
- Add subscription verification on app launch for iOS (StoreKit) and Android (Google Play Billing)
- Update SubscriptionApi to match Go backend endpoints (/subscription/purchase/)
- Update StoreKit Configuration with correct product IDs and pricing ($2.99/month, $27.99/year)
- Update Android placeholder prices to match App Store pricing
- Fix NotificationPreference model to match Go backend schema

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

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

composeApp/src/androidMain/kotlin/com/example/casera/MainActivity.kt

@@ -30,10 +30,12 @@ import com.example.casera.storage.ThemeStorage
 import com.example.casera.storage.ThemeStorageManager
 import com.example.casera.ui.theme.ThemeManager
 import com.example.casera.fcm.FCMManager
+import com.example.casera.platform.BillingManager
 import kotlinx.coroutines.launch
 
 class MainActivity : ComponentActivity(), SingletonImageLoader.Factory {
     private var deepLinkResetToken by mutableStateOf<String?>(null)
+    private lateinit var billingManager: BillingManager
 
     override fun onCreate(savedInstanceState: Bundle?) {
         enableEdgeToEdge()
@@ -49,12 +51,18 @@ class MainActivity : ComponentActivity(), SingletonImageLoader.Factory {
         ThemeStorage.initialize(ThemeStorageManager.getInstance(applicationContext))
         ThemeManager.initialize()
 
+        // Initialize BillingManager for subscription management
+        billingManager = BillingManager.getInstance(applicationContext)
+
         // Handle deep link from intent
         handleDeepLink(intent)
 
         // Request notification permission and setup FCM
         setupFCM()
 
+        // Verify subscriptions if user is authenticated
+        verifySubscriptionsOnLaunch()
+
         setContent {
             App(
                 deepLinkResetToken = deepLinkResetToken,
@@ -65,6 +73,36 @@ class MainActivity : ComponentActivity(), SingletonImageLoader.Factory {
         }
     }
 
+    /**
+     * Verify subscriptions with Google Play and sync with backend on app launch
+     */
+    private fun verifySubscriptionsOnLaunch() {
+        val authToken = TokenStorage.getToken()
+        if (authToken == null) {
+            Log.d("MainActivity", "No auth token, skipping subscription verification")
+            return
+        }
+
+        Log.d("MainActivity", "🔄 Verifying subscriptions on launch...")
+
+        billingManager.startConnection(
+            onSuccess = {
+                Log.d("MainActivity", "✅ Billing connected, restoring purchases...")
+                lifecycleScope.launch {
+                    val restored = billingManager.restorePurchases()
+                    if (restored) {
+                        Log.d("MainActivity", "✅ Subscriptions verified and synced with backend")
+                    } else {
+                        Log.d("MainActivity", "📦 No active subscriptions found")
+                    }
+                }
+            },
+            onError = { error ->
+                Log.e("MainActivity", "❌ Failed to connect to billing: $error")
+            }
+        )
+    }
+
     private fun setupFCM() {
         // Request notification permission if needed
         if (!FCMManager.isNotificationPermissionGranted(this)) {
@@ -86,9 +124,15 @@ class MainActivity : ComponentActivity(), SingletonImageLoader.Factory {
             val authToken = TokenStorage.getToken()
             if (authToken != null) {
                 val notificationApi = com.example.casera.network.NotificationApi()
+                val deviceId = android.provider.Settings.Secure.getString(
+                    contentResolver,
+                    android.provider.Settings.Secure.ANDROID_ID
+                )
                 val request = com.example.casera.models.DeviceRegistrationRequest(
+                    deviceId = deviceId,
                     registrationId = fcmToken,
-                    platform = "android"
+                    platform = "android",
+                    name = android.os.Build.MODEL
                 )
 
                 when (val result = notificationApi.registerDevice(authToken, request)) {

composeApp/src/androidMain/kotlin/com/example/casera/MyFirebaseMessagingService.kt

@@ -33,9 +33,15 @@ class MyFirebaseMessagingService : FirebaseMessagingService() {
                 val authToken = com.example.casera.storage.TokenStorage.getToken()
                 if (authToken != null) {
                     val notificationApi = com.example.casera.network.NotificationApi()
+                    val deviceId = android.provider.Settings.Secure.getString(
+                        applicationContext.contentResolver,
+                        android.provider.Settings.Secure.ANDROID_ID
+                    )
                     val request = com.example.casera.models.DeviceRegistrationRequest(
+                        deviceId = deviceId,
                         registrationId = token,
-                        platform = "android"
+                        platform = "android",
+                        name = android.os.Build.MODEL
                     )
 
                     when (val result = notificationApi.registerDevice(authToken, request)) {

composeApp/src/androidMain/kotlin/com/example/casera/platform/BillingManager.kt

@@ -350,6 +350,8 @@ class BillingManager private constructor(private val context: Context) {
                     true
                 } else {
                     Log.d(TAG, "No active purchases to restore")
+                    // Still fetch subscription status from backend to get free tier limits
+                    APILayer.getSubscriptionStatus(forceRefresh = true)
                     false
                 }
             } else {