feat: 实现PIPL数据主体删除权支持功能

- 新增 LeadDeletionRequest 模型，支持邮箱验证的删除申请/确认流程
- POST /api/v1/custom/leads/deletion-requests/ 发起申请（通用响应避免探测邮箱是否存在）
- POST /api/v1/custom/leads/deletion-requests/confirm/ 确认删除（24小时token有效期）
- 按邮箱在 Lead.data 中匹配并删除对应记录，跨SQLite/Postgres使用Python级匹配
- LeadDeletionRequest 通过 Django Admin 只读展示供合规审计
- 新增 FRONTEND_BASE_URL 设置用于拼接邮件确认链接
- apps/forms/tests.py 新增6个测试用例（含节流缓存隔离修复），全仓库30个用例通过
- 更新设计文档 §2.15/§2.16 勾选项

apps/forms/migrations/0002_leaddeletionrequest.py

@@ -0,0 +1,32 @@
+# Generated by Django 6.0.5 on 2026-08-07 05:13
+
+import uuid
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('forms', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='LeadDeletionRequest',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('contact', models.EmailField(max_length=254, verbose_name='联系邮箱')),
+                ('token', models.UUIDField(default=uuid.uuid4, editable=False, unique=True, verbose_name='确认令牌')),
+                ('status', models.CharField(choices=[('pending', '待确认'), ('completed', '已完成'), ('expired', '已过期')], default='pending', max_length=20, verbose_name='状态')),
+                ('requested_at', models.DateTimeField(auto_now_add=True, verbose_name='申请时间')),
+                ('confirmed_at', models.DateTimeField(blank=True, null=True, verbose_name='确认时间')),
+                ('completed_at', models.DateTimeField(blank=True, null=True, verbose_name='完成时间')),
+                ('deleted_count', models.PositiveIntegerField(default=0, verbose_name='已删除记录数')),
+            ],
+            options={
+                'verbose_name': '数据删除申请（PIPL）',
+                'verbose_name_plural': '数据删除申请（PIPL）',
+                'ordering': ['-requested_at'],
+            },
+        ),
+    ]