feat: add notification throttling and release build dry-run defaults

Author: JOHN

app/src/main/java/to/bitkit/paykit/PaykitFeatureFlags.kt

@@ -112,12 +112,16 @@ object PaykitFeatureFlags {
     private fun setDefaults() {
         prefs?.let { p ->
             if (!p.contains(ENABLED_KEY)) {
+                // Dry-run is enabled by default only in debug builds.
+                // In release builds, real payments execute immediately.
+                val dryRunDefault = to.bitkit.BuildConfig.DEBUG
+
                 p.edit()
                     .putBoolean(ENABLED_KEY, false) // Disabled by default until ready
                     .putBoolean(LIGHTNING_ENABLED_KEY, true)
                     .putBoolean(ONCHAIN_ENABLED_KEY, true)
                     .putBoolean(RECEIPT_STORAGE_ENABLED_KEY, true)
-                    .putBoolean(DRY_RUN_KEY, true) // Dry-run enabled by default for safety
+                    .putBoolean(DRY_RUN_KEY, dryRunDefault)
                     .apply()
             }
         }

app/src/main/java/to/bitkit/paykit/workers/SubscriptionCheckWorker.kt

@@ -343,12 +343,24 @@ class SubscriptionCheckWorker @AssistedInject constructor(
 
     /**
      * Schedule notifications for upcoming subscription payments.
+     * Notifications are throttled to once per subscription per billing period.
      */
     private fun scheduleUpcomingNotifications() {
         val upcomingSubscriptions = getUpcomingSubscriptions(withinHours = 24)
+        val prefs = appContext.getSharedPreferences("subscription_notifications", Context.MODE_PRIVATE)
 
         for (subscription in upcomingSubscriptions) {
+            val nextDue = subscription.nextPaymentAt ?: continue
+            val notificationKey = "notified_${subscription.id}_${nextDue}"
+
+            // Check if we've already notified for this billing cycle
+            if (prefs.getBoolean(notificationKey, false)) {
+                continue
+            }
+
+            // Send notification and mark as notified
             sendUpcomingPaymentNotification(subscription)
+            prefs.edit().putBoolean(notificationKey, true).apply()
         }
     }