fix: block legacy subscription renewal bypass in tariff mode

When switching from configurator to tariff mode, users with old
subscriptions (tariff_id=NULL) could still renew them through
unguarded paths, bypassing tariff pricing entirely.

Vulnerable paths fixed:
- MiniApp POST /subscription/renewal/options: returns empty list
  for classic subscriptions in tariff mode
- MiniApp POST /subscription/renewal: raises 400 with
  classic_subscription_blocked error code
- Bot confirm_extend_subscription: blocks stale extend_period_
  callbacks with tariff mode check
- Monitoring _process_autopayments: skips classic subscriptions
  (tariff_id=NULL) in autopay loop when tariff mode active

Already protected (no changes needed):
- Cabinet GET/POST renewal endpoints (renewal.py:51,117)
- Auto-purchase service (_prepare_auto_extend_context:244)
- Bot handle_extend_subscription menu (purchase.py:1657)
- Tariff extend flow (tariff_purchase.py:2047)

app/handlers/subscription/purchase.py

@@ -1817,6 +1817,14 @@ async def confirm_extend_subscription(
     days = int(callback.data.split('_')[2])
     texts = get_texts(db_user.language)
 
+    # Block classic subscription renewal when tariff mode is active
+    if settings.is_tariffs_mode():
+        await callback.answer(
+            texts.t('TARIFF_MODE_RENEWAL_BLOCKED', '❌ Продление в этом режиме недоступно. Выберите тариф.'),
+            show_alert=True,
+        )
+        return
+
     # Валидация что период доступен для продления
     available_renewal_periods = settings.get_available_renewal_periods()
     if days not in available_renewal_periods:

app/services/monitoring_service.py

@@ -1075,6 +1075,15 @@ class MonitoringService:
                     )
                     continue
 
+                # Skip classic subscriptions (tariff_id=NULL) when tariff mode is active
+                if settings.is_tariffs_mode() and not sub.tariff_id:
+                    logger.debug(
+                        'Пропускаем классическую подписку без тарифа в autopay (tariff mode)',
+                        sub_id=sub.id,
+                        user_id=sub.user_id,
+                    )
+                    continue
+
                 days_before_expiry = (sub.end_date - current_time).days
                 if days_before_expiry <= min(sub.autopay_days_before or 3, 3):
                     autopay_subscriptions.append(sub)

app/webapi/routes/miniapp.py

@@ -5106,6 +5106,14 @@ async def get_subscription_renewal_options_endpoint(
     )
     _validate_subscription_id(payload.subscription_id, subscription)
 
+    # Block classic subscription renewal when tariff mode is active
+    if settings.is_tariffs_mode() and not subscription.tariff_id:
+        return MiniAppSubscriptionRenewalOptionsResponse(
+            periods=[],
+            balance_kopeks=getattr(user, 'balance_kopeks', 0),
+            balance_currency=(getattr(user, 'balance_currency', None) or 'RUB').upper(),
+        )
+
     periods, pricing_map, default_period_id = await _prepare_subscription_renewal_options(
         db,
         user,
@@ -5197,6 +5205,16 @@ async def submit_subscription_renewal_endpoint(
     )
     _validate_subscription_id(payload.subscription_id, subscription)
 
+    # Block classic subscription renewal when tariff mode is active
+    if settings.is_tariffs_mode() and not subscription.tariff_id:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail={
+                'code': 'classic_subscription_blocked',
+                'message': 'Classic subscriptions cannot be renewed. Please purchase a tariff.',
+            },
+        )
+
     period_days: int | None = None
     if payload.period_days is not None:
         try: