feat(reaction): 新增 reaction app 与数据模型

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

reaction/migrations/0001_initial.py

@@ -0,0 +1,33 @@
+# Generated by Django 6.0.4 on 2026-08-06 07:35
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        ('problem', '0014_problem_tag_ci_unique'),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Reaction',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('type', models.CharField(choices=[('too_easy', '太简单'), ('too_hard', '太难了'), ('confusing', '没看懂'), ('buggy', '题目有错'), ('learned', '学到了'), ('interesting', '有意思'), ('want_explain', '想听讲解')], max_length=20, verbose_name='表情类型')),
+                ('create_time', models.DateTimeField(auto_now_add=True)),
+                ('problem', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='problem.problem')),
+                ('user', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
+            ],
+            options={
+                'db_table': 'reaction',
+                'indexes': [models.Index(fields=['problem', 'type'], name='reaction_problem_type_idx')],
+                'unique_together': {('problem', 'user', 'type')},
+            },
+        ),
+    ]