Fix HTTP 500 on the create pages with ?return=detail

UserCreate and AliasCreate used BackToUsersMixin and BackToAliasesMixin,
which access self.user or self.alias for ?return=detail. Neither exists
on the create pages, so the request failed with an AttributeError.

Both views now define their own back link with the target they already
used without the parameter: the user list and the user's detail page.

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

max/routes/alias/create.py

@@ -1,22 +1,22 @@
-from flask import flash
+from flask import flash, url_for
 
 from max.db import EmailAlreadyExists, create_alias, get_domains
 from max.permissions import AllowAdminOrSelf
 from max.translations import t
 
-from ..base_alias_views import BackToAliasesMixin
 from ..base_user_views import FetchUserTemplateGetView
 from ..check_email_mixin import CheckEmailMixin
 
 
-class AliasCreate(
-    AllowAdminOrSelf, CheckEmailMixin, BackToAliasesMixin, FetchUserTemplateGetView
-):
+class AliasCreate(AllowAdminOrSelf, CheckEmailMixin, FetchUserTemplateGetView):
     template_name = "alias/create.html"
 
     def get_webpagetitle(self):
         return f"Create new alias for {self.user.email}"
 
+    def get_back_text_and_url(self):
+        return self.user.email, url_for("user-detail", user_id=self.user.id)
+
     def post(self):
         error = False
         email = self.request.form.get("email")