feat(orders): implement QA audit fixes — return flow, refund webhook, TS cleanup

Convex backend (AUDIT-5–10):
- schema: add returnLabelUrl, returnTrackingNumber, returnCarrier fields +
  by_return_tracking_number_and_carrier and by_stripe_payment_intent_id indexes
- orders: markReturnReceived now sets status="completed"; add getOrderByPaymentIntent
  and applyReturnAccepted internal helpers
- returnActions: add acceptReturn action — creates Shippo return label (is_return:true),
  persists label data, sends return label email to customer
- stripeActions: handle refund.updated webhook to auto-mark orders refunded via Stripe Dashboard
- shippoWebhook: add getOrderByReturnTracking; applyTrackingUpdate extended with
  isReturnTracking flag (return events use return_tracking_update type, skip delivered transition)
- emails: add sendReturnLabelEmail; fulfillmentActions: createShippingLabel action

Admin UI (AUDIT-1–6):
- OrderActionsBar: full rewrite per authoritative action matrix; remove UpdateStatusDialog;
  add AcceptReturnButton for delivered+returnRequested state
- AcceptReturnButton: new action component matching CreateLabelButton pattern
- FulfilmentCard: add returnLabelUrl prop; show "Return label" row; rename outbound
  label to "Outbound label" when both are present
- statusConfig: add return_accepted to OrderEventType and EVENT_TYPE_LABELS
- orders detail page and all supporting cards/components

Storefront & shared (TS fixes):
- checkout/success, CheckoutErrorState, OrderReviewStep, PaymentStep: replace
  Button as/color/isLoading/variant="flat" with HeroUI v3-compatible props
- ReviewList: isLoading → isPending for HeroUI v3 Button
- packages/utils: add return and completed entries to ORDER_STATUS_LABELS/COLORS

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

convex/stripeActions.ts

@@ -229,6 +229,26 @@ export const handleWebhook = internalAction({
           (event.data.object as Stripe.Checkout.Session).id,
         );
         break;
+      case "refund.updated": {
+        const refund = event.data.object as Stripe.Refund;
+        if (refund.status === "succeeded" && refund.payment_intent) {
+          const paymentIntentId =
+            typeof refund.payment_intent === "string"
+              ? refund.payment_intent
+              : refund.payment_intent.id;
+          const order = await ctx.runQuery(
+            internal.orders.getOrderByPaymentIntent,
+            { stripePaymentIntentId: paymentIntentId },
+          );
+          if (order && order.paymentStatus !== "refunded") {
+            await ctx.runMutation(internal.orders.applyRefund, {
+              id: order._id,
+              adminUserId: order.userId,
+            });
+          }
+        }
+        break;
+      }
       default:
         console.log("Unhandled Stripe event type:", event.type);
     }