public user IDs, plans priced by tutor cost, age-based tutor tone, self-service account deletion

- profile publicId ("User482917", accounts/public_id.py); admin shows and searches it
- plans API reports aiDailyQuota per plan and freeAiDailyQuota; migration 0007 sets the
  temporary prices (monthly 99,000 / yearly 990,000 toman, 5 tutor questions a day) unless
  an admin already edited the yearly plan
- tutor tone follows the learner's age (18+ gets an adult tone at any grade); notation
  still follows the grade's book; answer cache keyed by tone (prompt tutor-v12-age-tone)
- POST /api/user/delete: phone users confirm with a fresh SMS code (same checks as login,
  now shared in verify_phone_otp), guests type "حذف"; payment records are kept, demo
  accounts refused
- delete_users --skip-paid

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

subscription/serializers.py

@@ -11,10 +11,13 @@ class PlanSerializer(serializers.Serializer):
     durationDays = serializers.IntegerField(required=False)
     features = serializers.ListField(child=serializers.CharField())
     badge = serializers.CharField(allow_blank=True)
+    aiDailyQuota = serializers.IntegerField(help_text='سوال در روز از دستیار برای مشترکِ این پلن.')
 
 
 class PlansListResponseSerializer(serializers.Serializer):
     plans = PlanSerializer(many=True)
+    # تا کارتِ پلن بتواند بگوید «۵ سوال در روز (رایگان: ۳)» بی‌آن‌که عدد در فرانت هاردکد شود.
+    freeAiDailyQuota = serializers.IntegerField()
 
 
 class PurchaseRequestSerializer(serializers.Serializer):