Question packs removed at the root; all subscriptions 4 assistant questions a day; Bazaar is subscription-only

- subscription.0017/0018, payment.0013: pack plans deleted, QuestionCredit/HeartsPass models and Plan.kind /
  question_credits / hearts_days / Order.question_credits / hearts_days dropped. The only paid pack order was the
  company owner's test account (user 26).
- Assistant: no credit spending; quota is the daily cap only (free 2, every plan 4, gift subscription 4).
- Bazaar: verify_purchase is subscription-only (no inapp guess), start/purchase responses lose productType,
  verify refuses an order without a subscription. A paid order with no subscription now logs ERROR.
- Removed POST /api/payment/orders (internal; no caller). Its permission tests stay.
- Pack-based tests rewritten on subscriptions (refund, security, Bazaar token); pack-only test files deleted.
- docs: profit table for 4/day on both payment routes plus free users; handbook, operations, CLAUDE.md current.
949 tests green.

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

subscription/migrations/0018_remove_question_packs.py

@@ -0,0 +1,31 @@
+# Generated by Django 5.2.17 on 2026-10-12 16:48
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('subscription', '0017_no_question_packs'),
+    ]
+
+    operations = [
+        migrations.DeleteModel(
+            name='HeartsPass',
+        ),
+        migrations.DeleteModel(
+            name='QuestionCredit',
+        ),
+        migrations.RemoveField(
+            model_name='plan',
+            name='hearts_days',
+        ),
+        migrations.RemoveField(
+            model_name='plan',
+            name='kind',
+        ),
+        migrations.RemoveField(
+            model_name='plan',
+            name='question_credits',
+        ),
+    ]