feat: add Printify order submission and fulfilment tracking

Submit paid orders to Printify via provider API with idempotent
guards, Stripe address mapping, and error handling. Track fulfilment
status through submitted → processing → shipped → delivered via
webhook-driven updates (primary) and Oban Cron polling fallback.

- 9 fulfilment fields on orders (status, provider IDs, tracking, timestamps)
- OrderSubmissionWorker with retry logic, auto-enqueued after Stripe payment
- FulfilmentStatusWorker polls every 30 mins for missed webhook events
- Printify order webhook handlers (sent-to-production, shipment, delivered)
- Admin UI: fulfilment column in table, fulfilment card with tracking info,
  submit/retry and refresh buttons on order detail
- Mox provider mocking for test isolation (Provider.for_type configurable)
- 33 new tests (555 total), verified against real Printify API

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

lib/simpleshop_theme_web/controllers/stripe_webhook_controller.ex

@@ -2,6 +2,7 @@ defmodule SimpleshopThemeWeb.StripeWebhookController do
   use SimpleshopThemeWeb, :controller
 
   alias SimpleshopTheme.Orders
+  alias SimpleshopTheme.Orders.OrderSubmissionWorker
 
   require Logger
 
@@ -36,14 +37,24 @@ defmodule SimpleshopThemeWeb.StripeWebhookController do
         {:ok, order} = Orders.mark_paid(order, payment_intent_id)
 
         # Update shipping address if collected by Stripe
-        if session.shipping_details do
-          update_shipping(order, session.shipping_details)
-        end
+        order =
+          if session.shipping_details do
+            {:ok, updated} = update_shipping(order, session.shipping_details)
+            updated
+          else
+            order
+          end
 
         # Update customer email from Stripe session
-        if session.customer_details && session.customer_details.email do
-          Orders.update_order(order, %{customer_email: session.customer_details.email})
-        end
+        order =
+          if session.customer_details && session.customer_details.email do
+            {:ok, updated} =
+              Orders.update_order(order, %{customer_email: session.customer_details.email})
+
+            updated
+          else
+            order
+          end
 
         # Broadcast to success page via PubSub
         Phoenix.PubSub.broadcast(
@@ -52,6 +63,15 @@ defmodule SimpleshopThemeWeb.StripeWebhookController do
           {:order_paid, order}
         )
 
+        # Submit to fulfilment provider
+        if order.shipping_address && order.shipping_address != %{} do
+          OrderSubmissionWorker.enqueue(order.id)
+        else
+          Logger.warning(
+            "Order #{order.order_number} paid but no shipping address — manual submit needed"
+          )
+        end
+
         Logger.info("Order #{order.order_number} marked as paid")
     end
   end