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.ex

@@ -248,6 +248,7 @@ defmodule MvWeb.MemberLive.Show do
     # Calculate last and current cycle status from loaded cycles
     last_cycle_status = get_last_cycle_status(member)
     current_cycle_status = get_current_cycle_status(member)
+
     member =
       member
       |> Map.put(:last_cycle_status, last_cycle_status)