fix: 邮箱字段设置为唯一且必填，改善错误提示

后端改动：
- User.email 设置为 unique=True，确保每个邮箱只能注册一次
- 这样 SendCodeView 能正确查找到已注册的邮箱

前端改动：
- LoginView 增加详细的错误日志输出
- 捕获更多错误信息类型帮助调试

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

offer_backend/apps/accounts/migrations/0004_alter_user_email.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.20 on 2026-03-25 08:09
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('accounts', '0003_alter_user_phone'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='user',
+            name='email',
+            field=models.EmailField(max_length=254, unique=True),
+        ),
+    ]

offer_backend/apps/accounts/models.py

@@ -54,6 +54,7 @@ class User(AbstractUser):
         ('admin', '公司管理员'),
         ('seeker', '求职者'),
     ]
+    email = models.EmailField(unique=True)  # 设置邮箱为唯一且必填
     role = models.CharField(max_length=20, choices=ROLE_CHOICES, default='seeker')
     phone = models.CharField(max_length=20)
     organization = models.ForeignKey(

offer_frontend/src/views/auth/LoginView.vue

@@ -169,7 +169,12 @@ async function handleSendCode() {
     isLocked.value = false
     startCountdown()
   } catch (err) {
-    ElMessage.error(err.response?.data?.error || err.response?.data?.email?.[0] || '发送失败，请检查邮箱是否正确')
+    const errorMsg = err.response?.data?.error ||
+                     err.response?.data?.email?.[0] ||
+                     err.response?.data?.detail ||
+                     '发送失败，请检查邮箱是否正确'
+    console.error('SendCode Error:', err.response?.data)
+    ElMessage.error(errorMsg)
   } finally {
     sendingCode.value = false
   }