Payment providers as classes (Strategy + factory); 10342 = monthly; health logs a failed Bazaar check

- payment/providers.py: ZarinpalProvider / BazaarProvider with one interface (check_plan, sku_for, payment_url,
  purchase_extras, discount_blocker, reconcile_user); provider_for / provider_for_method pick one; unknown fails.
  create_order, purchase view, discount redeem and reconcile_user_orders use it instead of scattered ifs.
- subscription.0015: Bazaar SKU 10342 on the one-month plan (owner: "probably the monthly one").
- config/health: the Bazaar check no longer swallows its exception without a log.
982 tests green.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

subscription/serializers.py

@@ -30,7 +30,8 @@ class PurchaseRequestSerializer(serializers.Serializer):
     # از request.headers خونده می‌شه، نه از بدنه.
     planId = serializers.CharField()
     # تا ۲۰۲۶-۱۰-۰۳ هر مقداری پذیرفته و نادیده گرفته می‌شد، پس «bazaar» بی‌صدا به زرین‌پال می‌رفت.
-    paymentMethod = serializers.ChoiceField(choices=['zarinpal', 'bazaar'], required=False, default='zarinpal')
+    paymentMethod = serializers.ChoiceField(choices=['zarinpal', 'bazaar'], required=False, default='zarinpal',
+                                            help_text='payment/providers.py: هر مقدار یک کلاسِ PaymentProvider.')
 
 
 class PurchaseResponseSerializer(serializers.Serializer):