feat: prevent join requests with equal mail

lib/membership/join_request.ex

@@ -77,6 +77,17 @@ defmodule Mv.Membership.JoinRequest do
 
       change Mv.Membership.JoinRequest.Changes.RejectRequest
     end
+
+    # Internal: resend confirmation (new token) when user submits form again with same email.
+    # Called from domain with authorize?: false; not exposed to public.
+    update :regenerate_confirmation_token do
+      description "Set new confirmation token and expiry (resend flow)"
+      require_atomic? false
+
+      argument :confirmation_token, :string, allow_nil?: false
+
+      change Mv.Membership.JoinRequest.Changes.RegenerateConfirmationToken
+    end
   end
 
   policies do
@@ -175,6 +186,11 @@ defmodule Mv.Membership.JoinRequest do
     attribute :approved_at, :utc_datetime_usec
     attribute :rejected_at, :utc_datetime_usec
     attribute :reviewed_by_user_id, :uuid
+
+    attribute :reviewed_by_display, :string do
+      description "Denormalized reviewer display (e.g. email) for UI without loading User"
+    end
+
     attribute :source, :string
 
     create_timestamp :inserted_at