add CI pipeline with credo and dialyzer

mix ci alias: compile --warning-as-errors, format --check-formatted,
credo, dialyzer, test. Credo configured with sensible defaults.
Dialyzer ignore file for false positives (Stripe types, Mix tasks,
ExUnit internals). Credo fixes: map_join, filter consolidation,
nesting extraction, cond→if simplification.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/simpleshop_theme/orders/fulfilment_status_worker.ex

@@ -23,24 +23,27 @@ defmodule SimpleshopTheme.Orders.FulfilmentStatusWorker do
       Logger.info("Polling fulfilment status for #{length(orders)} order(s)")
 
       Enum.each(orders, fn order ->
-        case Orders.refresh_fulfilment_status(order) do
-          {:ok, updated} ->
-            if updated.fulfilment_status != order.fulfilment_status do
-              Logger.info(
-                "Order #{order.order_number} status: #{order.fulfilment_status} → #{updated.fulfilment_status}"
-              )
-            end
-
-          {:error, reason} ->
-            Logger.warning(
-              "Failed to refresh status for order #{order.order_number}: #{inspect(reason)}"
-            )
-        end
-
+        refresh_order(order)
         Process.sleep(200)
       end)
 
       :ok
     end
   end
+
+  defp refresh_order(order) do
+    case Orders.refresh_fulfilment_status(order) do
+      {:ok, updated} ->
+        if updated.fulfilment_status != order.fulfilment_status do
+          Logger.info(
+            "Order #{order.order_number} status: #{order.fulfilment_status} → #{updated.fulfilment_status}"
+          )
+        end
+
+      {:error, reason} ->
+        Logger.warning(
+          "Failed to refresh status for order #{order.order_number}: #{inspect(reason)}"
+        )
+    end
+  end
 end