Finishing a lesson or island needs recorded answers and an unlocked island; auto DB backup before migrate; throttles on 15 more routes

- content: POST nodes/{id}/quiz/complete and lessons/{id}/complete refuse a locked island
  (403 node_locked, same rule as /api/home) and a user who has not answered every question
  (409 answers_missing). Before, only a user with zero hearts and no answers was refused, so
  anyone else finished any island, locked or not, and finishing a locked island's lessons
  unlocked it. A node or lesson with no questions still passes when unlocked, with no XP.
  The client can no longer understate totalQuestions to buy stars.
- throttle_scope on 15 routes that had none (question bank without login, intro, hearts,
  notifications, tickets, plans, subscription status, orders, offers, affiliate, assistant
  history and feedback, logout).
- admin: OTPCode and Session can only be added/changed by a superuser.
- deploy.sh: integrity-checked DB backup before migrate (keeps the last 2); no migrate without it.
- docs and CLAUDE.md updated to say what is verified and what is not.

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

content/tests_flow.py

@@ -317,6 +317,8 @@ class LessonCompletionNotificationTests(TestCase):
 
         self.user = User.objects.create(phone='09000000009', grade_id=grade.id)
         from accounts.authentication import issue_access_token
+        from content.testing import record_answers
+        record_answers(self.user.id, lesson=self.lesson)  # پایانِ درس بی‌جواب پذیرفته نمی‌شود
         self.client.credentials(HTTP_AUTHORIZATION=f'Bearer {issue_access_token(self.user.id)}')
 
     def tearDown(self):