feat: add AST_CHECK_FAILED status, is_accepted helper, ast_rules field

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

submission/migrations/0007_alter_submission_result.py

@@ -0,0 +1,18 @@
+# Generated by Django 6.0.4 on 2026-05-26 02:36
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('submission', '0006_alter_submission_info_alter_submission_result_and_more'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='submission',
+            name='result',
+            field=models.IntegerField(choices=[(-2, 'Compile Error'), (-1, 'Wrong Answer'), (0, 'Accepted'), (1, 'CPU Time Limit Exceeded'), (2, 'Real Time Limit Exceeded'), (3, 'Memory Limit Exceeded'), (4, 'Runtime Error'), (5, 'System Error'), (6, 'Pending'), (7, 'Judging'), (8, 'Partially Accepted'), (10, 'AST Check Failed')], db_default=6, db_index=True, default=6),
+        ),
+    ]