feat: update frontend for unified order model

Update all frontend templates and JavaScript to use new unified Order model:
- Orders tab: use status field, processing/cancelled values, items array
- Order detail: use snapshot fields, items array, tracking_provider
- JavaScript: update API params (status vs sync_status), orderStats fields
- Tracking modal: use tracking_provider instead of tracking_carrier
- Order items modal: use items array with item_state field

All status mappings:
- pending → pending (unconfirmed)
- processing → confirmed (at least one item available)
- cancelled → declined (all items unavailable)
- shipped → shipped (with tracking)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/admin/js/marketplace-letzshop.js

@@ -92,7 +92,7 @@ function adminMarketplaceLetzshop() {
         ordersFilter: '',
         ordersSearch: '',
         ordersHasDeclinedItems: false,
-        orderStats: { pending: 0, confirmed: 0, rejected: 0, shipped: 0, has_declined_items: 0 },
+        orderStats: { pending: 0, processing: 0, shipped: 0, delivered: 0, cancelled: 0, total: 0, has_declined_items: 0 },
 
         // Jobs
         jobs: [],
@@ -103,7 +103,7 @@ function adminMarketplaceLetzshop() {
         showTrackingModal: false,
         showOrderModal: false,
         selectedOrder: null,
-        trackingForm: { tracking_number: '', tracking_carrier: '' },
+        trackingForm: { tracking_number: '', tracking_provider: '' },
 
         async init() {
             marketplaceLetzshopLog.info('init() called');
@@ -399,7 +399,7 @@ function adminMarketplaceLetzshop() {
                 });
 
                 if (this.ordersFilter) {
-                    params.append('sync_status', this.ordersFilter);
+                    params.append('status', this.ordersFilter);
                 }
 
                 if (this.ordersHasDeclinedItems) {
@@ -437,13 +437,14 @@ function adminMarketplaceLetzshop() {
          */
         updateOrderStats() {
             // Reset stats
-            this.orderStats = { pending: 0, confirmed: 0, rejected: 0, shipped: 0, has_declined_items: 0 };
+            this.orderStats = { pending: 0, processing: 0, shipped: 0, delivered: 0, cancelled: 0, total: 0, has_declined_items: 0 };
 
             // Count from orders list (only visible page - not accurate for totals)
             for (const order of this.orders) {
-                if (this.orderStats.hasOwnProperty(order.sync_status)) {
-                    this.orderStats[order.sync_status]++;
+                if (this.orderStats.hasOwnProperty(order.status)) {
+                    this.orderStats[order.status]++;
                 }
+                this.orderStats.total++;
             }
         },
 
@@ -669,7 +670,7 @@ function adminMarketplaceLetzshop() {
             this.selectedOrder = order;
             this.trackingForm = {
                 tracking_number: order.tracking_number || '',
-                tracking_carrier: order.tracking_carrier || ''
+                tracking_provider: order.tracking_provider || ''
             };
             this.showTrackingModal = true;
         },
@@ -707,17 +708,24 @@ function adminMarketplaceLetzshop() {
         },
 
         /**
-         * Confirm a single inventory unit
+         * Confirm a single order item
          */
-        async confirmInventoryUnit(order, unit, index) {
+        async confirmInventoryUnit(order, item, index) {
             if (!this.selectedVendor) return;
 
+            // Use external_item_id (Letzshop inventory unit ID)
+            const itemId = item.external_item_id;
+            if (!itemId) {
+                this.error = 'Item has no external ID';
+                return;
+            }
+
             try {
                 await apiClient.post(
-                    `/admin/letzshop/vendors/${this.selectedVendor.id}/orders/${order.id}/items/${unit.id}/confirm`
+                    `/admin/letzshop/vendors/${this.selectedVendor.id}/orders/${order.id}/items/${itemId}/confirm`
                 );
                 // Update local state
-                this.selectedOrder.inventory_units[index].state = 'confirmed_available';
+                this.selectedOrder.items[index].item_state = 'confirmed_available';
                 this.successMessage = 'Item confirmed';
                 // Reload orders to get updated status
                 await this.loadOrders();
@@ -728,17 +736,24 @@ function adminMarketplaceLetzshop() {
         },
 
         /**
-         * Decline a single inventory unit
+         * Decline a single order item
          */
-        async declineInventoryUnit(order, unit, index) {
+        async declineInventoryUnit(order, item, index) {
             if (!this.selectedVendor) return;
 
+            // Use external_item_id (Letzshop inventory unit ID)
+            const itemId = item.external_item_id;
+            if (!itemId) {
+                this.error = 'Item has no external ID';
+                return;
+            }
+
             try {
                 await apiClient.post(
-                    `/admin/letzshop/vendors/${this.selectedVendor.id}/orders/${order.id}/items/${unit.id}/decline`
+                    `/admin/letzshop/vendors/${this.selectedVendor.id}/orders/${order.id}/items/${itemId}/decline`
                 );
                 // Update local state
-                this.selectedOrder.inventory_units[index].state = 'confirmed_unavailable';
+                this.selectedOrder.items[index].item_state = 'confirmed_unavailable';
                 this.successMessage = 'Item declined';
                 // Reload orders to get updated status
                 await this.loadOrders();