fix: reworking some code smell issues

lib/bds/strings.ex

@@ -0,0 +1,9 @@
+defmodule BDS.Strings do
+  @moduledoc """
+  Small string-formatting helpers shared across the codebase.
+  """
+
+  @doc "Zero-pads an integer to at least two digits, e.g. `3 -> \"03\"`."
+  @spec pad2(integer()) :: String.t()
+  def pad2(value), do: value |> Integer.to_string() |> String.pad_leading(2, "0")
+end