senior's post-demo changes: parent report in the student's own account, Jalali birth date, invoices, math-only tutor, priced quotas

- remove the family app from the root (separate parent accounts, invite codes, parental
  settings); progress.0006 drops its tables, permissions and migration history, and
  Profile.parent_phone, the two family notification types and ?userId= on
  /api/progress/nodes go with it
- GET /api/user/weekly-report: last 7 days next to the 7 before (estimated minutes,
  questions, accuracy, islands, tutor questions) for the "parent report" page
- profile birthDate in Jalali (accounts/jalali.py), ages 5-99, birthYear derived from it
- GET /api/payment/invoices; orders now snapshot list price and plan title
- tutor answers only math: server pre-filter, scope rule in the prompt (tutor-v11),
  refusal marker replaced with fixed text; self-harm gets a help line instead
- streamed answers now record token usage (it was always 0)
- daily tutor quota: AI_DAILY_QUOTA_FREE (default 3) vs Plan.ai_daily_quota
- delete_users management command for wiping test accounts across every app
- docs/ai-cost-and-guardrails.md: measured cost per question and guardrail results

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

ai_tutor/tests_quota.py

@@ -0,0 +1,53 @@
+"""
+سقفِ روزانه‌ی دستیار: رایگان در برابرِ اشتراکی (۲۰۲۶-۱۰-۰۱). تا آن روز همه ۱۵ سوال
+داشتند، یعنی گران‌ترین بخشِ اپ برای کاربرِ بی‌اشتراک هم کامل باز بود.
+"""
+from datetime import timedelta
+
+from django.core.cache import cache
+from django.test import TestCase, override_settings
+from django.utils import timezone
+from rest_framework.test import APIClient
+
+from accounts.authentication import issue_access_token
+from accounts.models import User
+from subscription.models import Plan, Subscription
+from subscription.services import ai_daily_quota
+
+
+@override_settings(AI_DAILY_QUOTA_FREE=2)
+class DailyQuotaTests(TestCase):
+    def setUp(self):
+        cache.clear()
+        self.user = User.objects.create(phone='09120006001', is_guest=False)
+        self.client = APIClient()
+        self.client.credentials(HTTP_AUTHORIZATION=f'Bearer {issue_access_token(self.user.id)}')
+
+    def ask(self):
+        return self.client.post('/api/ai/ask', {'userQuestion': '۲ + ۲ چند میشه؟'}, format='json')
+
+    def test_free_user_gets_the_free_quota_and_a_hint_to_subscribe(self):
+        self.assertEqual([self.ask().status_code for _ in range(2)], [200, 200])
+        blocked = self.ask()
+        self.assertEqual(blocked.status_code, 429)
+        self.assertIn('اشتراک', blocked.json()['detail'])
+
+    def test_remaining_quota_follows_the_users_own_limit(self):
+        self.assertEqual(self.ask().json()['remainingQuota'], 1)
+
+    def test_subscriber_gets_the_plans_quota(self):
+        plan = Plan.objects.create(title='ماهانه', price=99000, duration_days=30, ai_daily_quota=4)
+        Subscription.objects.create(user_id=self.user.id, plan=plan, status='active',
+                                    expires_at=timezone.now() + timedelta(days=30))
+        self.assertEqual(ai_daily_quota(self.user.id), 4)
+        self.assertEqual([self.ask().status_code for _ in range(5)], [200, 200, 200, 200, 429])
+
+    def test_expired_subscription_falls_back_to_free(self):
+        plan = Plan.objects.create(title='ماهانه', price=99000, duration_days=30, ai_daily_quota=40)
+        Subscription.objects.create(user_id=self.user.id, plan=plan, status='active',
+                                    expires_at=timezone.now() - timedelta(days=1))
+        self.assertEqual(ai_daily_quota(self.user.id), 2)
+
+    def test_gifted_subscription_without_plan_gets_the_default(self):
+        Subscription.objects.create(user_id=self.user.id, plan=None, status='active', expires_at=None)
+        self.assertEqual(ai_daily_quota(self.user.id), 15)