feat: add marketplace products admin UI with copy-to-vendor functionality

- Add admin marketplace products page to browse imported products
- Add admin vendor products page to manage vendor catalog
- Add product detail pages for both marketplace and vendor products
- Implement copy-to-vendor API to copy marketplace products to vendor catalogs
- Add vendor product service with CRUD operations
- Update sidebar navigation with new product management links
- Add integration and unit tests for new endpoints and services

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

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

static/admin/js/marketplace-product-detail.js

@@ -0,0 +1,181 @@
+// static/admin/js/marketplace-product-detail.js
+/**
+ * Admin marketplace product detail page logic
+ * View and manage individual marketplace products
+ */
+
+const adminMarketplaceProductDetailLog = window.LogConfig.loggers.adminMarketplaceProductDetail ||
+    window.LogConfig.createLogger('adminMarketplaceProductDetail', false);
+
+adminMarketplaceProductDetailLog.info('Loading...');
+
+function adminMarketplaceProductDetail() {
+    adminMarketplaceProductDetailLog.info('adminMarketplaceProductDetail() called');
+
+    // Extract product ID from URL
+    const pathParts = window.location.pathname.split('/');
+    const productId = parseInt(pathParts[pathParts.length - 1]);
+
+    return {
+        // Inherit base layout state
+        ...data(),
+
+        // Set page identifier
+        currentPage: 'marketplace-products',
+
+        // Product ID from URL
+        productId: productId,
+
+        // Loading states
+        loading: true,
+        error: '',
+
+        // Product data
+        product: null,
+
+        // Copy to vendor modal state
+        showCopyModal: false,
+        copying: false,
+        copyForm: {
+            vendor_id: '',
+            skip_existing: true
+        },
+        targetVendors: [],
+
+        async init() {
+            adminMarketplaceProductDetailLog.info('Marketplace Product Detail init() called, ID:', this.productId);
+
+            // Guard against multiple initialization
+            if (window._adminMarketplaceProductDetailInitialized) {
+                adminMarketplaceProductDetailLog.warn('Already initialized, skipping');
+                return;
+            }
+            window._adminMarketplaceProductDetailInitialized = true;
+
+            // Load data in parallel
+            await Promise.all([
+                this.loadProduct(),
+                this.loadTargetVendors()
+            ]);
+
+            adminMarketplaceProductDetailLog.info('Marketplace Product Detail initialization complete');
+        },
+
+        /**
+         * Load product details
+         */
+        async loadProduct() {
+            this.loading = true;
+            this.error = '';
+
+            try {
+                const response = await apiClient.get(`/admin/products/${this.productId}`);
+                this.product = response;
+                adminMarketplaceProductDetailLog.info('Loaded product:', this.product.marketplace_product_id);
+            } catch (error) {
+                adminMarketplaceProductDetailLog.error('Failed to load product:', error);
+                this.error = error.message || 'Failed to load product details';
+            } finally {
+                this.loading = false;
+            }
+        },
+
+        /**
+         * Load target vendors for copy functionality
+         */
+        async loadTargetVendors() {
+            try {
+                const response = await apiClient.get('/admin/vendors?is_active=true&limit=500');
+                this.targetVendors = response.vendors || [];
+                adminMarketplaceProductDetailLog.info('Loaded target vendors:', this.targetVendors.length);
+            } catch (error) {
+                adminMarketplaceProductDetailLog.error('Failed to load target vendors:', error);
+            }
+        },
+
+        /**
+         * Open copy modal
+         */
+        openCopyModal() {
+            this.copyForm.vendor_id = '';
+            this.showCopyModal = true;
+            adminMarketplaceProductDetailLog.info('Opening copy modal for product:', this.productId);
+        },
+
+        /**
+         * Execute copy to vendor catalog
+         */
+        async executeCopyToVendor() {
+            if (!this.copyForm.vendor_id) {
+                this.error = 'Please select a target vendor';
+                return;
+            }
+
+            this.copying = true;
+            try {
+                const response = await apiClient.post('/admin/products/copy-to-vendor', {
+                    marketplace_product_ids: [this.productId],
+                    vendor_id: parseInt(this.copyForm.vendor_id),
+                    skip_existing: this.copyForm.skip_existing
+                });
+
+                adminMarketplaceProductDetailLog.info('Copy result:', response);
+
+                // Show success message
+                const copied = response.copied || 0;
+                const skipped = response.skipped || 0;
+                const failed = response.failed || 0;
+
+                let message;
+                if (copied > 0) {
+                    message = 'Product successfully copied to vendor catalog.';
+                } else if (skipped > 0) {
+                    message = 'Product already exists in the vendor catalog.';
+                } else {
+                    message = 'Failed to copy product.';
+                }
+
+                // Close modal
+                this.showCopyModal = false;
+
+                // Show notification
+                Utils.showToast(message, copied > 0 ? 'success' : 'warning');
+            } catch (error) {
+                adminMarketplaceProductDetailLog.error('Failed to copy product:', error);
+                this.error = error.message || 'Failed to copy product to vendor catalog';
+            } finally {
+                this.copying = false;
+            }
+        },
+
+        /**
+         * Format price for display
+         */
+        formatPrice(price, currency = 'EUR') {
+            if (price === null || price === undefined) return '-';
+            return new Intl.NumberFormat('en-US', {
+                style: 'currency',
+                currency: currency || 'EUR'
+            }).format(price);
+        },
+
+        /**
+         * Format date for display
+         */
+        formatDate(dateString) {
+            if (!dateString) return '-';
+            try {
+                const date = new Date(dateString);
+                return date.toLocaleDateString('en-US', {
+                    year: 'numeric',
+                    month: 'short',
+                    day: 'numeric',
+                    hour: '2-digit',
+                    minute: '2-digit'
+                });
+            } catch (e) {
+                return dateString;
+            }
+        }
+    };
+}