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>

content/views.py

@@ -741,7 +741,9 @@ class NodeProgressListView(APIView):
         qs = NodeProgress.objects.filter(user_id=request.user.id).select_related('node')
         unit_id = request.query_params.get('unit')
         if unit_id:
-            qs = qs.filter(node__unit_id=unit_id)
+            if not unit_id.isdigit():
+                raise ValidationError({'unit': 'شناسه‌ی فصل باید عدد باشد.'})
+            qs = qs.filter(node__unit_id=int(unit_id))
 
         data = {'progress': list(qs.order_by('node__unit_id', 'node__order'))}
         return Response(NodeProgressListResponseSerializer(data).data)