refactor: fix credo warnings and format code

- Replace Enum.map/2 |> Enum.join/2 with Enum.map_join/3 for efficiency
- Refactor get_existing_form_values to reduce cyclomatic complexity
- Replace length/1 with Enum.empty?/1 for better performance
- Update gettext translations

lib/mv_web/live/member_live/show/membership_fees_component.ex

@@ -39,7 +39,9 @@ defmodule MvWeb.MemberLive.Show.MembershipFeesComponent do
               </span>
             </div>
           <% else %>
-            <span class="text-base-content/60 italic">{gettext("No membership fee type assigned")}</span>
+            <span class="text-base-content/60 italic">
+              {gettext("No membership fee type assigned")}
+            </span>
           <% end %>
         </div>
 
@@ -369,9 +371,7 @@ defmodule MvWeb.MemberLive.Show.MembershipFeesComponent do
 
       {:error, %Ash.Error.Invalid{} = error} ->
         error_msg =
-          error.errors
-          |> Enum.map(fn e -> e.message end)
-          |> Enum.join(", ")
+          Enum.map_join(error.errors, ", ", fn e -> e.message end)
 
         {:noreply,
          socket
@@ -424,7 +424,6 @@ defmodule MvWeb.MemberLive.Show.MembershipFeesComponent do
     end
   end
 
-
   def handle_event("edit_cycle_amount", %{"cycle_id" => cycle_id}, socket) do
     cycle = find_cycle(socket.assigns.cycles, cycle_id)