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>

docs/operations.md

@@ -60,8 +60,10 @@ curl -i https://mathapi.tadrisino2.ir/api/health
 
 ## بکاپ و بازیابی
 
-`db.sqlite3` در گیت **نیست** و تنها نسخه‌ی داده‌ی کاربران است. `deploy.sh`
-پیش از `migrate` بکاپ نمی‌گیرد؛ تا وقتی این خودکار نشده، دستی بگیرید:
+`db.sqlite3` در گیت **نیست** و تنها نسخه‌ی داده‌ی کاربران است. `deploy.sh` پیش از `migrate`
+خودش بکاپ می‌گیرد (`.deploy-backups/db-before-deploy-<زمان>.sqlite3`، با `integrity_check`، ۲ تای
+آخر نگه داشته می‌شود) و اگر بکاپ نشد migrate را اجرا نمی‌کند. این بکاپ روی همان ماشین است؛ نسخه‌ی
+بیرون از ماشین هنوز نیست. برای بکاپِ دستی (مثلاً پیش از تغییرِ `.env` یا کارِ ادمین):
 
 ```bash
 cd /home/administrator/mathapp-v2