Fix Credo nesting in Splynx MRR calculation

Extract parse_mrr/1 helper to reduce nesting depth in calculate_total_mrr.
Credo --strict: 0 issues. Dialyzer: pass (no new warnings).

lib/towerops/splynx/sync.ex

@@ -47,23 +47,21 @@ defmodule Towerops.Splynx.Sync do
   end
 
   defp calculate_total_mrr(customers) do
-    Enum.reduce(customers, 0.0, fn customer, total ->
-      case customer["mrr_total"] do
-        value when is_binary(value) ->
-          case Float.parse(value) do
-            {num, _} -> total + num
-            :error -> total
-          end
-
-        value when is_number(value) ->
-          total + value
-
-        _ ->
-          total
-      end
-    end)
+    customers
+    |> Enum.map(&parse_mrr/1)
+    |> Enum.sum()
   end
 
+  defp parse_mrr(%{"mrr_total" => value}) when is_binary(value) do
+    case Float.parse(value) do
+      {num, _} -> num
+      :error -> 0.0
+    end
+  end
+
+  defp parse_mrr(%{"mrr_total" => value}) when is_number(value), do: value
+  defp parse_mrr(_), do: 0.0
+
   defp humanize_sync_error(:unauthorized), do: "Authentication failed — check your API key and secret"
   defp humanize_sync_error(:forbidden), do: "Access denied — your API credentials may not have sufficient permissions"
   defp humanize_sync_error({:rate_limited, retry_after}), do: "Rate limited by Splynx — retry after #{retry_after}s"