Paywall: first unit of each grade free; 1/3/6-month subscriptions; AI sold separately

- content: unit_is_free/has_unit_access; questions, node quiz, answer and lesson/node
  complete return 402 subscription_required outside the first unit without an active
  subscription. /api/home units carry requiresSubscription.
- subscription.0013: monthly 498k, quarterly 798k, six-month 1,298k toman, unlimited
  hearts, 3 AI questions/day; packs stay on sale for more questions.
- AI_DAILY_QUOTA_FREE default 3 -> 2.
- /api/subscription/status adds planTitle, planDurationDays, aiDailyQuota.
- tests: content/tests_paywall.py; existing unlock-order tests get a subscription.

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

subscription/tests.py

@@ -486,7 +486,7 @@ class YearlyPlanSeedTests(TestCase):
         self.assertTrue(plan.features)
 
     def test_a_monthly_plan_is_created_next_to_it(self):
-        plan = Plan.objects.get(duration_days=30)
+        plan = Plan.objects.get(duration_days=30, on_sale=False)
         self.assertEqual((plan.price, plan.ai_daily_quota), (179_000, 10))
 
     def test_repricing_leaves_an_admin_edited_yearly_plan_alone(self):
@@ -498,16 +498,20 @@ class YearlyPlanSeedTests(TestCase):
         importlib.import_module('subscription.migrations.0008_paid_quota_ten_a_day').apply(global_apps, None)
         plan = Plan.objects.get(title='اشتراک یک‌ساله')
         self.assertEqual((plan.price, plan.ai_daily_quota), (450_000, 9))
-        self.assertEqual(Plan.objects.filter(duration_days=30).count(), 1)
+        self.assertEqual(Plan.objects.filter(duration_days=30, on_sale=False).count(), 1)
 
-    def test_only_question_packs_are_on_sale(self):
+    def test_packs_and_new_subscriptions_are_on_sale(self):
         from django.core.cache import cache
         cache.clear()
         data = self.client.get('/api/subscription/plans').json()
-        self.assertEqual({p['kind'] for p in data['plans']}, {'pack'})
-        self.assertEqual([p['questionCredits'] for p in data['plans']], [20, 60, 150])
-        self.assertEqual([p['heartsDays'] for p in data['plans']], [7, 30, 60])
-        self.assertEqual(data['freeAiDailyQuota'], 3)
+        packs = [p for p in data['plans'] if p['kind'] == 'pack']
+        subs = [p for p in data['plans'] if p['kind'] == 'subscription']
+        self.assertEqual([p['questionCredits'] for p in packs], [20, 60, 150])
+        self.assertEqual([p['heartsDays'] for p in packs], [7, 30, 60])
+        # subscription.0013: یک/سه/شش‌ماهه با سقفِ ۳ سوال در روز.
+        self.assertEqual([(p['durationDays'], p['price'], p['aiDailyQuota']) for p in subs],
+                         [(30, 498_000, 3), (90, 798_000, 3), (180, 1_298_000, 3)])
+        self.assertEqual(data['freeAiDailyQuota'], 2)
         # پلن‌های اشتراکی پاک نشده‌اند؛ فقط فروخته نمی‌شوند.
         self.assertFalse(Plan.objects.get(title='اشتراک یک‌ساله').on_sale)