feat: redesign Letzshop products tab with product listing view

Products Tab Changes:
- Converted to product listing page similar to /admin/marketplace-products
- Added Import/Export buttons in header
- Added product stats cards (total, active, inactive, last sync)
- Added search and filter functionality
- Added product table with pagination
- Import modal for single URL or all languages

Settings Tab Changes:
- Moved batch size setting from products tab
- Moved include inactive checkbox from products tab
- Added export behavior info box

Export Changes:
- New POST endpoint exports all languages (FR, DE, EN)
- CSV files written to exports/letzshop/{vendor_code}/ for scheduler pickup
- Letzshop scheduler can fetch files from this location

API Changes:
- Added vendor_id filter to /admin/vendor-products/stats endpoint
- Added POST /admin/vendors/{id}/export/letzshop for folder export

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

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

app/templates/admin/partials/letzshop-settings-tab.html

@@ -1,5 +1,6 @@
 {# app/templates/admin/partials/letzshop-settings-tab.html #}
-{# Settings tab for admin Letzshop management - API credentials and CSV URLs #}
+{# Settings tab for admin Letzshop management - API credentials, CSV URLs, Import/Export settings #}
+{% from 'shared/macros/inputs.html' import number_stepper %}
 
 <div class="grid gap-6 lg:grid-cols-2">
     <!-- API Configuration Card -->
@@ -236,6 +237,75 @@
         </div>
     </div>
 
+    <!-- Import/Export Settings Card -->
+    <div class="bg-white rounded-lg shadow-xs dark:bg-gray-800">
+        <div class="p-6">
+            <h3 class="mb-4 text-lg font-semibold text-gray-700 dark:text-gray-200">
+                Import / Export Settings
+            </h3>
+            <p class="text-sm text-gray-600 dark:text-gray-400 mb-6">
+                Configure settings for product import and export operations.
+            </p>
+
+            <!-- Import Settings -->
+            <div class="mb-6">
+                <h4 class="text-sm font-medium text-gray-700 dark:text-gray-300 mb-3 flex items-center">
+                    <span x-html="$icon('cloud-download', 'w-4 h-4 mr-2 text-purple-500')"></span>
+                    Import Settings
+                </h4>
+                <div class="pl-6">
+                    <label class="block text-sm font-medium text-gray-700 dark:text-gray-400 mb-2">
+                        Batch Size
+                    </label>
+                    {{ number_stepper(model='importForm.batch_size', min=100, max=5000, step=100, label='Batch Size') }}
+                    <p class="mt-1 text-xs text-gray-500 dark:text-gray-400">
+                        Products processed per batch (100-5000). Higher = faster but more memory.
+                    </p>
+                </div>
+            </div>
+
+            <!-- Export Settings -->
+            <div class="border-t border-gray-200 dark:border-gray-600 pt-6">
+                <h4 class="text-sm font-medium text-gray-700 dark:text-gray-300 mb-3 flex items-center">
+                    <span x-html="$icon('upload', 'w-4 h-4 mr-2 text-green-500')"></span>
+                    Export Settings
+                </h4>
+                <div class="pl-6">
+                    <label class="flex items-center cursor-pointer">
+                        <input
+                            type="checkbox"
+                            x-model="exportIncludeInactive"
+                            class="form-checkbox h-5 w-5 text-purple-600 rounded border-gray-300 dark:border-gray-600 dark:bg-gray-700 focus:ring-purple-500"
+                        />
+                        <span class="ml-3 text-sm font-medium text-gray-700 dark:text-gray-400">Include inactive products</span>
+                    </label>
+                    <p class="mt-1 text-xs text-gray-500 dark:text-gray-400 ml-8">
+                        Export products that are currently marked as inactive
+                    </p>
+                </div>
+            </div>
+
+            <!-- Export Info Box -->
+            <div class="mt-6 p-4 bg-gray-50 dark:bg-gray-700 rounded-lg">
+                <h4 class="text-sm font-medium text-gray-700 dark:text-gray-300 mb-2">Export Behavior</h4>
+                <ul class="text-xs text-gray-500 dark:text-gray-400 space-y-1">
+                    <li class="flex items-center">
+                        <span x-html="$icon('check', 'w-3 h-3 mr-2 text-green-500')"></span>
+                        Exports all languages (FR, DE, EN) automatically
+                    </li>
+                    <li class="flex items-center">
+                        <span x-html="$icon('check', 'w-3 h-3 mr-2 text-green-500')"></span>
+                        CSV files are placed in a folder for Letzshop pickup
+                    </li>
+                    <li class="flex items-center">
+                        <span x-html="$icon('check', 'w-3 h-3 mr-2 text-green-500')"></span>
+                        Letzshop scheduler fetches files periodically
+                    </li>
+                </ul>
+            </div>
+        </div>
+    </div>
+
     <!-- Carrier Settings Card -->
     <div class="bg-white rounded-lg shadow-xs dark:bg-gray-800 lg:col-span-2">
         <div class="p-6">