chore: 将后端移动到 api/ 目录，准备合并为单仓库

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

api/task/migrations/0002_alter_task_display.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.1.6 on 2025-03-10 10:38
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('task', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='task',
+            name='display',
+            field=models.IntegerField(db_index=True, unique=True),
+        ),
+    ]