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>

accounts/tests_delete_users.py

@@ -0,0 +1,51 @@
+"""delete_users: کاربر و همه‌ی داده‌اش در همه‌ی اپ‌ها، و هیچ چیزِ کاربرِ دیگری."""
+from io import StringIO
+
+from django.core.management import CommandError, call_command
+from django.test import TestCase
+
+from accounts.models import OTPCode, Profile, User
+from ai_tutor.models import Conversation, Message
+from notifications.models import Notification
+from payment.models import Order
+from progress.models import UserStats
+
+
+class DeleteUsersTests(TestCase):
+    def setUp(self):
+        self.doomed = User.objects.create(phone='09121110001', is_guest=False)
+        self.kept = User.objects.create(phone='09121110002', is_guest=False)
+        for user in (self.doomed, self.kept):
+            Profile.objects.create(user=user)
+            UserStats.objects.create(user_id=user.id, xp=10)
+            Message.objects.create(conversation=Conversation.objects.create(user_id=user.id), role='user', text='؟')
+            Notification.objects.create(user_id=user.id, type='xp_earned', title='ت')
+            OTPCode.objects.create(phone=user.phone, code='123456', expires_at='2030-01-01T00:00Z')
+
+    def run_command(self, *args):
+        out = StringIO()
+        call_command('delete_users', *args, stdout=out)
+        return out.getvalue()
+
+    def test_dry_run_changes_nothing(self):
+        out = self.run_command('--phones', self.doomed.phone)
+        self.assertIn('progress.UserStats.user_id: 1', out)
+        self.assertTrue(User.objects.filter(pk=self.doomed.pk).exists())
+
+    def test_everything_of_that_user_goes_and_nothing_else(self):
+        self.run_command('--phones', self.doomed.phone, '--yes')
+        self.assertFalse(User.objects.filter(pk=self.doomed.pk).exists())
+        for model in (UserStats, Conversation, Notification):
+            self.assertFalse(model.objects.filter(user_id=self.doomed.pk).exists(), model)
+            self.assertTrue(model.objects.filter(user_id=self.kept.pk).exists(), model)
+        self.assertFalse(OTPCode.objects.filter(phone=self.doomed.phone).exists())
+        self.assertTrue(OTPCode.objects.filter(phone=self.kept.phone).exists())
+        self.assertEqual(Message.objects.count(), 1)
+
+    def test_paid_orders_need_explicit_permission(self):
+        Order.objects.create(user_id=self.doomed.id, amount=1000, status='paid', idempotency_key='k1')
+        with self.assertRaises(CommandError):
+            self.run_command('--ids', str(self.doomed.pk), '--yes')
+        self.assertTrue(User.objects.filter(pk=self.doomed.pk).exists())
+        self.run_command('--ids', str(self.doomed.pk), '--yes', '--include-paid')
+        self.assertFalse(Order.objects.filter(user_id=self.doomed.pk).exists())