replace setup checklist with interactive stepper

3-step vertical stepper with inline forms for Printify and Stripe,
real-time sync progress via PubSub, and celebration state on go-live.

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

lib/simpleshop_theme/sync/product_sync_worker.ex

@@ -66,6 +66,7 @@ defmodule SimpleshopTheme.Sync.ProductSyncWorker do
   defp sync_products(conn) do
     Logger.info("Starting product sync for #{conn.provider_type} (#{conn.id})")
     Products.update_sync_status(conn, "syncing")
+    broadcast_sync(conn.id, {:sync_status, "syncing"})
 
     try do
       do_sync_products(conn)
@@ -73,6 +74,7 @@ defmodule SimpleshopTheme.Sync.ProductSyncWorker do
       e ->
         Logger.error("Product sync crashed for #{conn.provider_type}: #{Exception.message(e)}")
         Products.update_sync_status(conn, "failed")
+        broadcast_sync(conn.id, {:sync_status, "failed"})
         {:error, :sync_crashed}
     end
   end
@@ -95,11 +97,14 @@ defmodule SimpleshopTheme.Sync.ProductSyncWorker do
       )
 
       Products.update_sync_status(conn, "completed", DateTime.utc_now())
+      product_count = Products.count_products_for_connection(conn.id)
+      broadcast_sync(conn.id, {:sync_status, "completed", product_count})
       :ok
     else
       {:error, reason} = error ->
         Logger.error("Product sync failed for #{conn.provider_type}: #{inspect(reason)}")
         Products.update_sync_status(conn, "failed")
+        broadcast_sync(conn.id, {:sync_status, "failed"})
         error
     end
   end
@@ -146,6 +151,10 @@ defmodule SimpleshopTheme.Sync.ProductSyncWorker do
     Products.upsert_product(conn, attrs)
   end
 
+  defp broadcast_sync(conn_id, message) do
+    Phoenix.PubSub.broadcast(SimpleshopTheme.PubSub, "sync:#{conn_id}", message)
+  end
+
   defp sync_product_associations(product, product_data) do
     # Sync images
     images =