Bazaar: subscriptions (10343/10344), dynamic price (discount codes on Bazaar), auto-renewal sync

- Purchase with paymentMethod=bazaar now works for subscription plans with a bazaar_sku (not only packs);
  response carries bazaarProductType. Migration subscription.0014 puts 10343/10344 on the 90/180-day plans.
- Verify asks Bazaar for the right product type (from the order) and stores validUntil (payment.0012).
- POST /api/payment/bazaar/orders/{id}/start: SKU, type, and an HS256 dynamic-price JWT when a discount
  code lowered the price (BAZAAR_DYNAMIC_PRICE_KEY); discount on Bazaar orders allowed only with that key
  and only before start.
- Auto-renewal: sync_bazaar_renewals re-asks Bazaar when the paid period is near its end (status page and
  the paywall via has_subscription_access); each new period becomes a paid order.
- Default BAZAAR_PACKAGE_NAME = com.tadrisino.math.app; health shows bazaarDynamicPrice.
979 tests green. No real Bazaar purchase or renewal tested.

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

payment/urls.py

@@ -1,6 +1,7 @@
 from django.urls import path
 
 from .views import (
+    BazaarStartPurchaseView,
     BazaarVerifyPurchaseView,
     CreateOrderView,
     InvoiceListView,
@@ -13,6 +14,8 @@ urlpatterns = [
     path('payment/orders', CreateOrderView.as_view(), name='payment-create-order'),
     path('payment/zarinpal/callback', ZarinpalCallbackView.as_view(), name='payment-zarinpal-callback'),
     path('payment/bazaar/verify', BazaarVerifyPurchaseView.as_view(), name='payment-bazaar-verify'),
+    path('payment/bazaar/orders/<int:order_id>/start', BazaarStartPurchaseView.as_view(),
+         name='payment-bazaar-start'),
     path('payment/invoices', InvoiceListView.as_view(), name='payment-invoices'),
     path('payment/orders/<int:order_id>', OrderDetailView.as_view(), name='payment-order-detail'),
     path('payment/orders/<int:order_id>/pay', PaymentRedirectView.as_view(), name='payment-order-pay'),