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>

content/tests_hearts_gate.py

@@ -32,7 +32,7 @@ def _client(user):
 class _World:
     def build(self, phone):
         cache.clear()
-        self.user = User.objects.create(phone=phone, is_guest=False)
+        self.user = User.objects.create(phone=phone)
         self.client = _client(self.user)
         grade = Grade.objects.create(title='پایه نهم', icon='', color='')
         self.node = Node.objects.create(unit=Unit.objects.create(grade=grade, title='فصل', order=1),