senior's post-demo changes: parent report in the student's own account, Jalali birth date, invoices, math-only tutor, priced quotas

- remove the family app from the root (separate parent accounts, invite codes, parental
  settings); progress.0006 drops its tables, permissions and migration history, and
  Profile.parent_phone, the two family notification types and ?userId= on
  /api/progress/nodes go with it
- GET /api/user/weekly-report: last 7 days next to the 7 before (estimated minutes,
  questions, accuracy, islands, tutor questions) for the "parent report" page
- profile birthDate in Jalali (accounts/jalali.py), ages 5-99, birthYear derived from it
- GET /api/payment/invoices; orders now snapshot list price and plan title
- tutor answers only math: server pre-filter, scope rule in the prompt (tutor-v11),
  refusal marker replaced with fixed text; self-harm gets a help line instead
- streamed answers now record token usage (it was always 0)
- daily tutor quota: AI_DAILY_QUOTA_FREE (default 3) vs Plan.ai_daily_quota
- delete_users management command for wiping test accounts across every app
- docs/ai-cost-and-guardrails.md: measured cost per question and guardrail results

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

subscription/services.py

@@ -19,6 +19,26 @@ def has_unlimited_hearts(user_id: int) -> bool:
     ).exists()
 
 
+# اشتراکِ بی‌پلن (هدیه/آفر با grant_free_subscription) همان سقفِ پیش‌فرضِ پلن را می‌گیرد.
+DEFAULT_SUBSCRIBER_AI_QUOTA = 15
+
+
+def ai_daily_quota(user_id: int) -> int:
+    """
+    سقفِ سوالِ روزانه از دستیار برای این کاربر: بیشترینِ سقفِ پلن‌های اشتراکِ فعالش،
+    یا AI_DAILY_QUOTA_FREE اگر اشتراکِ فعال ندارد. تا ۲۰۲۶-۱۰-۰۱ همه ۱۵ سوال داشتند،
+    با اشتراک یا بی‌اشتراک — یعنی دستیار، گران‌ترین بخشِ اپ، رایگان بود.
+    """
+    from django.conf import settings
+
+    now = timezone.now()
+    active = Subscription.objects.filter(user_id=user_id, status='active').filter(
+        models.Q(expires_at__isnull=True) | models.Q(expires_at__gt=now))
+    quotas = [s.plan.ai_daily_quota if s.plan else DEFAULT_SUBSCRIBER_AI_QUOTA
+              for s in active.select_related('plan')]
+    return max(quotas) if quotas else settings.AI_DAILY_QUOTA_FREE
+
+
 def activate_subscription(subscription_id: int, plan_id: int | None = None):
     """
     بعد از تاییدِ پرداخت صدا زده می‌شود (کال‌بکِ زرین‌پال، تاییدِ بازار).