Audit fixes 2026-10-03: seed keeps admin edits, plan cache, refresh limit, payment and tutor guards

- seed_content no longer undoes admin work: a SeedRecord ledger (content/seed_sync.py)
  stops deleted/renamed/re-worded content from being recreated and keeps admin-edited
  lesson text; new rows in the seed files still arrive (migration content.0010)
- plan list cache is invalidated on Plan save (receiver used a stale 'v1' key)
- token refresh per-IP cap 30/hour -> 600/hour (TOKEN_REFRESH_IP_RATE)
- a failed gateway result only changes a pending order (forged NOK no longer
  overwrites refunded/canceled)
- tutor gets the correct answer only after the student has answered
- support reply notification moved to a TicketMessage post_save signal
- global daily cap on paid AI questions (AI_GLOBAL_DAILY_MAX, default 3000)
- Bazaar verify uses only the order's SKU; bazaar orders require a SKU
- /api/health warns on the committed signing key; deploy.sh saves local commits;
  400 for bad ?unit= / ?period=; account delete keeps the referrer's Conversion
- earlier today: no stub answers outside DEBUG, ?grade= removed, logged fallbacks

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

progress/views.py

@@ -140,6 +140,10 @@ class LeaderboardView(APIView):
     )
     def get(self, request):
         period = request.query_params.get('period', 'weekly')
+        from .leaderboard import PERIODS
+        if period not in PERIODS:
+            # پیش‌تر هر رشته‌ای ۲۰۰ و یک کلیدِ کشِ تازه می‌ساخت.
+            raise ValidationError({'period': f'یکی از {", ".join(PERIODS)}.'})
 
         # زنده از فعالیتِ واقعی، با کشِ کوتاه (progress/leaderboard.py). قبلاً از
         # جدولِ LeaderboardEntry خوانده می‌شد که فقط با اجرای دستیِ