feat: prominent ML shipping config error message + skip-validation checkbox

- Add skip-validation checkbox for accounts where ML validation fails due to config
- Detect 'User has not mode' errors and show detailed actionable help box
- Include direct links to ML seller config and support

pos/static/js/inventory.js

@@ -1068,7 +1068,20 @@
         var success = (data.success || []).length;
         var failedList = data.failed || [];
         var failed = failedList.length;
+        var hasModeError = failedList.some(function(f) { return (f.error || '').toLowerCase().indexOf('user has not mode') !== -1; });
         var html = '<div style="margin-bottom:var(--space-2);"><span style="color:var(--color-success);">✅ ' + success + ' publicado(s)</span> · <span style="color:var(--color-error);">❌ ' + failed + ' fallo(s)</span></div>';
+        if (hasModeError) {
+            html += '<div style="background:var(--color-surface-2);border:1px solid var(--color-error);border-radius:var(--radius-md);padding:var(--space-3);margin:var(--space-2) 0;font-size:var(--text-caption);color:var(--color-text-primary);">' +
+                '<strong>⚠️ Tu cuenta de MercadoLibre no tiene modos de envío configurados.</strong><br>' +
+                'Esto es un requisito de MercadoLibre, no de Nexus.<br>' +
+                'Pasos para solucionarlo:<br>' +
+                '1. Entrá a <a href="https://www.mercadolibre.com.mx" target="_blank" style="color:var(--color-primary);text-decoration:underline;">mercadolibre.com.mx</a> con la cuenta de vendedor<br>' +
+                '2. Andá a <strong>Vender &gt; Configuración de envíos</strong><br>' +
+                '3. Completá tu dirección de retiro y activá al menos un método de envío<br>' +
+                '4. Si no te aparece la opción, contactá a <a href="https://www.mercadolibre.com.mx/ayuda" target="_blank" style="color:var(--color-primary);text-decoration:underline;">soporte de MercadoLibre</a><br>' +
+                '<em>Nota: Algunas cuentas nuevas necesitan verificar identidad antes de poder configurar envíos.</em>' +
+                '</div>';
+        }
         if (failedList.length) {
             html += '<ul style="margin:0;padding-left:var(--space-4);font-size:var(--text-caption);color:var(--color-text-secondary);">';
             failedList.forEach(function(f) {

pos/templates/inventory.html

@@ -882,6 +882,10 @@
             <label>Costo de Envío (MXN)</label>
             <input type="number" id="meliShippingCost" value="150" min="0" step="1" />
           </div>
+          <div class="inv-field" style="display:flex;align-items:center;gap:8px;margin-top:var(--space-2);">
+            <input type="checkbox" id="meliSkipValidate" style="width:auto;height:auto;" />
+            <label for="meliSkipValidate" style="margin:0;font-size:var(--text-caption);color:var(--color-text-muted);text-transform:none;">Saltear validación y publicar directamente (si la validación falla por config de cuenta)</label>
+          </div>
         </div>
 
         <!-- Dynamic required attributes section -->
@@ -914,7 +918,7 @@
   <script src="/pos/static/js/pos-utils.js" defer></script>
   <script src="/pos/static/js/sidebar.js" defer></script>
   <script src="/pos/static/js/virtual-scroll.js?v=2" defer></script>
-  <script src="/pos/static/js/inventory.js?v=14" defer></script>
+  <script src="/pos/static/js/inventory.js?v=15" defer></script>
   <script src="/pos/static/js/offline-banner.js" defer></script>
   <script src="/pos/static/js/sync-engine.js" defer></script>
   <script>if('serviceWorker' in navigator){navigator.serviceWorker.register('/pos/sw.js',{scope:'/pos/'});}</script>