feat: add email notice and settings page but still have some issue

src/backend/email_notice/admin.py

@@ -0,0 +1,22 @@
+from django.contrib import admin
+from .models import NotificationEmail, NotificationSettings
+
+@admin.register(NotificationEmail)
+class NotificationEmailAdmin(admin.ModelAdmin):
+    list_display = ('email', 'is_enabled', 'description', 'created_at')
+    list_filter = ('is_enabled', 'created_at')
+    search_fields = ('email', 'description')
+    list_editable = ('is_enabled',)
+    ordering = ('-created_at',)
+
+@admin.register(NotificationSettings)
+class NotificationSettingsAdmin(admin.ModelAdmin):
+    list_display = ('email_notification_enabled', 'updated_at')
+
+    def has_add_permission(self, request):
+        # 只允许存在一个设置实例
+        return not NotificationSettings.objects.exists()
+
+    def has_delete_permission(self, request, obj=None):
+        # 不允许删除设置
+        return False