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/models.py

@@ -26,6 +26,11 @@ class Plan(models.Model):
     # برچسبِ بالای کارت: «محبوب‌ترین»، «بهترین ارزش». `popular` فقط بولین است
     # و یک متن نمی‌دهد؛ این جایگزینش نیست، کنارش است.
     badge = models.CharField(max_length=30, blank=True)
+    # چند سوال در روز از دستیار. هر سوال حدودِ ۰٫۲ سنتِ دلار (~۶۰۰ تومان) هزینه‌ی API
+    # دارد (docs/ai-cost-and-guardrails.md)، پس این عدد مستقیم سودِ پلن را تعیین می‌کند.
+    # کاربرِ بدونِ اشتراک سقفِ AI_DAILY_QUOTA_FREE (settings) را دارد.
+    ai_daily_quota = models.PositiveSmallIntegerField(
+        default=15, help_text='سقفِ سوالِ روزانه از دستیارِ هوش مصنوعی برای مشترکانِ این پلن.')
 
     def __str__(self):
         return self.title