Remove the guest system entirely: no is_guest/device_id, no guest throttles, phone login is the only way in

accounts.0008 drops the columns and refuses to run while guest rows exist.
Docs describe the current state; tests that only proved guest behaviour are gone.

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

rag/tests_tutor_quality.py

@@ -183,7 +183,7 @@ class ConversationMemoryTests(TestCase):
         cache.clear()
 
     def _user(self, phone):
-        user = User.objects.create(phone=phone, is_guest=False)
+        user = User.objects.create(phone=phone)
         client = APIClient()
         client.credentials(HTTP_AUTHORIZATION=f'Bearer {issue_access_token(user.id)}')
         return client
@@ -231,7 +231,7 @@ class ProviderStateTests(TestCase):
     def setUp(self):
         cache.clear()
         reset_clients_cache()
-        user = User.objects.create(phone='09120000904', is_guest=False)
+        user = User.objects.create(phone='09120000904')
         self.client = APIClient()
         self.client.credentials(HTTP_AUTHORIZATION=f'Bearer {issue_access_token(user.id)}')
 
@@ -276,7 +276,7 @@ class QuestionFocusTests(TestCase):
                                                 type='multiple_choice', prompt='۲ به توان منفی ۳؟')
         self.right = Choice.objects.create(question=self.question, value='1/8', is_correct=True)
         self.wrong = Choice.objects.create(question=self.question, value='-8', is_correct=False)
-        user = User.objects.create(phone='09120000905', is_guest=False, grade_id=grade.id)
+        user = User.objects.create(phone='09120000905', grade_id=grade.id)
         self.client = APIClient()
         self.client.credentials(HTTP_AUTHORIZATION=f'Bearer {issue_access_token(user.id)}')