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_audit_fixes.py

@@ -141,23 +141,6 @@ class HeartsTests(TestCase):
         self.assertEqual(response.json()['code'], 'no_hearts')
 
 
-class FamilyTwoChildrenTests(TestCase):
-    def test_a_parent_of_two_can_see_each_child(self):
-        parent = User.objects.create(phone='09121234010', is_guest=False)
-        kids = []
-        for phone in ('09121234011', '09121234012'):
-            kid = User.objects.create(phone=phone, is_guest=False)
-            code = _client(parent).post('/api/family/link/invite', {'childPhone': phone},
-                                        format='json').json()['inviteCode']
-            _client(kid).post('/api/family/link/accept', {'inviteCode': code}, format='json')
-            kids.append(kid)
-        client = _client(parent)
-        self.assertEqual(client.get('/api/family/settings').status_code, 200)
-        self.assertEqual(client.get('/api/family/weekly-report').status_code, 200)
-        self.assertEqual(client.get(f'/api/family/settings?childUserId={kids[0].id}').status_code, 200)
-        self.assertEqual(client.get('/api/family/settings?childUserId=999999').status_code, 404)
-
-
 class AdminLoginThrottleTests(TestCase):
     def setUp(self):
         cache.clear()