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/vendor-product-detail.js

@@ -0,0 +1,170 @@
+// static/admin/js/vendor-product-detail.js
+/**
+ * Admin vendor product detail page logic
+ * View and manage individual vendor catalog products
+ */
+
+const adminVendorProductDetailLog = window.LogConfig.loggers.adminVendorProductDetail ||
+    window.LogConfig.createLogger('adminVendorProductDetail', false);
+
+adminVendorProductDetailLog.info('Loading...');
+
+function adminVendorProductDetail() {
+    adminVendorProductDetailLog.info('adminVendorProductDetail() 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: 'vendor-products',
+
+        // Product ID from URL
+        productId: productId,
+
+        // Loading states
+        loading: true,
+        error: '',
+
+        // Product data
+        product: null,
+
+        // Modals
+        showRemoveModal: false,
+        removing: false,
+
+        async init() {
+            adminVendorProductDetailLog.info('Vendor Product Detail init() called, ID:', this.productId);
+
+            // Guard against multiple initialization
+            if (window._adminVendorProductDetailInitialized) {
+                adminVendorProductDetailLog.warn('Already initialized, skipping');
+                return;
+            }
+            window._adminVendorProductDetailInitialized = true;
+
+            // Load product data
+            await this.loadProduct();
+
+            adminVendorProductDetailLog.info('Vendor Product Detail initialization complete');
+        },
+
+        /**
+         * Load product details
+         */
+        async loadProduct() {
+            this.loading = true;
+            this.error = '';
+
+            try {
+                const response = await apiClient.get(`/admin/vendor-products/${this.productId}`);
+                this.product = response;
+                adminVendorProductDetailLog.info('Loaded product:', this.product.id);
+            } catch (error) {
+                adminVendorProductDetailLog.error('Failed to load product:', error);
+                this.error = error.message || 'Failed to load product details';
+            } finally {
+                this.loading = false;
+            }
+        },
+
+        /**
+         * Open edit modal (placeholder for future implementation)
+         */
+        openEditModal() {
+            window.dispatchEvent(new CustomEvent('toast', {
+                detail: { message: 'Edit functionality coming soon', type: 'info' }
+            }));
+        },
+
+        /**
+         * Toggle active status
+         */
+        async toggleActive() {
+            // TODO: Implement PATCH endpoint for status update
+            window.dispatchEvent(new CustomEvent('toast', {
+                detail: {
+                    message: 'Status toggle functionality coming soon',
+                    type: 'info'
+                }
+            }));
+        },
+
+        /**
+         * Confirm remove
+         */
+        confirmRemove() {
+            this.showRemoveModal = true;
+        },
+
+        /**
+         * Execute remove
+         */
+        async executeRemove() {
+            this.removing = true;
+
+            try {
+                await apiClient.delete(`/admin/vendor-products/${this.productId}`);
+
+                adminVendorProductDetailLog.info('Product removed:', this.productId);
+
+                window.dispatchEvent(new CustomEvent('toast', {
+                    detail: {
+                        message: 'Product removed from catalog successfully',
+                        type: 'success'
+                    }
+                }));
+
+                // Redirect to vendor products list
+                setTimeout(() => {
+                    window.location.href = '/admin/vendor-products';
+                }, 1000);
+            } catch (error) {
+                adminVendorProductDetailLog.error('Failed to remove product:', error);
+                window.dispatchEvent(new CustomEvent('toast', {
+                    detail: { message: error.message || 'Failed to remove product', type: 'error' }
+                }));
+            } finally {
+                this.removing = false;
+                this.showRemoveModal = false;
+            }
+        },
+
+        /**
+         * Format price for display
+         */
+        formatPrice(price, currency = 'EUR') {
+            if (price === null || price === undefined) return '-';
+            const numPrice = typeof price === 'string' ? parseFloat(price) : price;
+            if (isNaN(numPrice)) return price;
+
+            return new Intl.NumberFormat('de-DE', {
+                style: 'currency',
+                currency: currency || 'EUR'
+            }).format(numPrice);
+        },
+
+        /**
+         * Format date for display
+         */
+        formatDate(dateString) {
+            if (!dateString) return '-';
+            try {
+                const date = new Date(dateString);
+                return date.toLocaleDateString('en-GB', {
+                    year: 'numeric',
+                    month: 'short',
+                    day: 'numeric',
+                    hour: '2-digit',
+                    minute: '2-digit'
+                });
+            } catch (e) {
+                return dateString;
+            }
+        }
+    };
+}