Subscriptions only: Bazaar panel prices (598/898/1398k), assistant quota 5/3/3 from a cost calculation, packs off sale

- subscription.0016: prices equal to the Bazaar panel (senior), ai_daily_quota 5/3/3, card features; packs on_sale=False
  (one paid pack order, user 26, keeps its credits; pack paths stay for that order and for admin).
- Quota math in docs/ai-cost-and-guardrails.md: ~77% of a Bazaar sale reaches us; worst case (full quota every day)
  the assistant costs 23/27/35% of it.
- Assistant quota message points to the subscription, not packs.
982 tests green.

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

subscription/tests_security_review.py

@@ -24,6 +24,7 @@ class PaidPackWithDeletedPlanTests(TestCase):
         app = APIClient()
         app.credentials(HTTP_AUTHORIZATION=f'Bearer {issue_access_token(user.id)}')
         pack = Plan.objects.get(kind='pack', question_credits=20)
+        Plan.objects.filter(pk=pack.pk).update(on_sale=True)  # بسته‌ها از subscription.0016 فروشی نیستند
         order = Order.objects.get(pk=app.post('/api/subscription/purchase', {'planId': str(pack.id)},
                                               format='json').json()['orderId'])
         pack.delete()