Seed: grade 3 rebuilt (every lesson 5+ questions, wrong figures/lesson text fixed), Persian digits and plain fractions across all grades, apply_fixups gains lesson/question_set, ledger save chunked for SQLite

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

content/seed_sync.py

@@ -57,7 +57,11 @@ class _Ledger:
             self.write[key] = (kind, value)
 
     def save(self) -> None:
-        existing = set(SeedRecord.objects.filter(key__in=list(self.write)).values_list('key', flat=True))
+        # دسته‌دسته: SQLite بیش از ۳۲٬۷۶۶ متغیر در یک پرس‌وجو نمی‌پذیرد و دفترِ یک seedِ تازه از آن بیشتر است.
+        keys = list(self.write)
+        existing = set()
+        for i in range(0, len(keys), 500):
+            existing.update(SeedRecord.objects.filter(key__in=keys[i:i + 500]).values_list('key', flat=True))
         SeedRecord.objects.bulk_create([
             SeedRecord(key=k, kind=kind, value=value)
             for k, (kind, value) in self.write.items() if k not in existing