feat: MercadoLibre integration + inventory bulk publish + WhatsApp bridge fixes

- Add MercadoLibre OAuth, listings, orders, webhooks and category search
- New marketplace_external_bp.py, meli_service.py, marketplace_external_service.py
- New marketplace_external.html/js with ML management UI
- Inventory: bulk publish to ML with category autocomplete, listing type and shipping selectors
- Inventory: new .btn--meli styles, select/label CSS fixes
- WhatsApp bridge: rate limiting, 440/515/408 error handling, stale watchdog
- DB migration v3.4_meli_integration.sql for marketplace_listings, orders, sync_queue
- Add Celery tasks for ML sync and webhook processing
- Sidebar: MercadoLibre navigation link

pos/templates/marketplace.html

@@ -57,10 +57,11 @@
     <h2 style="margin-bottom:var(--space-4);font-family:var(--font-heading);">Mi Inventario</h2>
     <div class="upload-box">
       <label>Cargar inventario via CSV</label>
-      <textarea id="csvText" placeholder="part_number,stock,price&#10;AB-123,5,150.50&#10;CD-456,12,89.00"></textarea>
+      <textarea id="csvText" placeholder="part_number,stock,price,name&#10;AB-123,5,150.50,Filtro de aceite&#10;CD-456,12,89.00,Balata delantera"></textarea>
       <div class="hint">
         Columnas requeridas: <code>part_number, stock, price</code>.
-        Opcionales: <code>min_order, warehouse_location, currency</code>.
+        Opcionales: <code>name, min_order, warehouse_location, currency</code>.
+        <br>Si la parte no existe en el catálogo, se crea automáticamente como <em>seller listing</em>.
       </div>
       <button style="margin-top:var(--space-3);padding:var(--space-3) var(--space-6);background:var(--gradient-accent);color:var(--btn-primary-text);border:none;border-radius:var(--radius-md);font-weight:bold;cursor:pointer;" onclick="uploadCSV()">Subir CSV</button>
       <div id="uploadResult" style="margin-top:var(--space-3);font-size:var(--text-body-sm);"></div>
@@ -205,8 +206,18 @@
           var priceStr = p.min_price === p.max_price
             ? '$' + fmt(p.min_price)
             : '$' + fmt(p.min_price) + ' – $' + fmt(p.max_price);
-          return '<div class="part-card" onclick="openPartDetail(' + p.id_part + ')">' +
-            '<div class="part-card__oem">' + esc(p.oem_part_number) + '</div>' +
+          var isOem = p.listing_type === 'oem';
+          var badge = isOem
+            ? '<span style="background:#3FB95020;color:#3FB950;padding:2px 6px;border-radius:4px;font-size:var(--text-caption);">Catálogo</span>'
+            : '<span style="background:#F5A62320;color:#F5A623;padding:2px 6px;border-radius:4px;font-size:var(--text-caption);">Listing</span>';
+          var onclick = isOem
+            ? 'openPartDetail(' + p.id + ')'
+            : 'openListingDetail(' + p.id + ')';
+          return '<div class="part-card" onclick="' + onclick + '">' +
+            '<div style="display:flex;justify-content:space-between;align-items:center;margin-bottom:var(--space-1);">' +
+              '<div class="part-card__oem">' + esc(p.part_number) + '</div>' +
+              badge +
+            '</div>' +
             '<div class="part-card__name">' + esc(p.name) + '</div>' +
             '<div class="part-card__meta">' +
               '<span class="price-range">' + priceStr + '</span>' +
@@ -248,7 +259,7 @@
             '</div>' +
             '<div style="text-align:right;">' +
               '<div class="price-range">$' + fmt(b.price) + '</div>' +
-              '<button style="margin-top:var(--space-1);padding:var(--space-1) var(--space-3);background:var(--gradient-accent);color:var(--btn-primary-text);border:none;border-radius:var(--radius-sm);font-size:var(--text-caption);cursor:pointer;" onclick="createOrderFor(' + partId + ', ' + b.id_bodega + ', \'' + esc(b.name).replace(/\'/g, '\\\'') + '\', ' + (b.price || 0) + ')">Ordenar</button>' +
+              '<button style="margin-top:var(--space-1);padding:var(--space-1) var(--space-3);background:var(--gradient-accent);color:var(--btn-primary-text);border:none;border-radius:var(--radius-sm);font-size:var(--text-caption);cursor:pointer;" onclick="createOrderFor(' + partId + ', null, ' + b.id_bodega + ', \'' + esc(b.name).replace(/\'/g, '\\\'') + '\', ' + (b.price || 0) + ')">Ordenar</button>' +
             '</div>' +
           '</div>';
         });
@@ -257,7 +268,38 @@
       });
     };
 
-    window.createOrderFor = function (partId, bodegaId, bodegaName, price) {
+    window.openListingDetail = function (wiId) {
+      var modal = document.getElementById('partModal');
+      modal.classList.add('open');
+      document.getElementById('partModalBody').innerHTML = 'Cargando bodegas...';
+
+      apiFetch('/inventory/listing/' + wiId).then(function (resp) {
+        if (!resp || !resp.data) return;
+        var bodegas = resp.data;
+        if (bodegas.length === 0) {
+          document.getElementById('partModalBody').innerHTML = '<div class="empty-state">Ninguna bodega tiene esta parte en stock.</div>';
+          return;
+        }
+        var html = '<p style="color:var(--color-text-muted);margin-bottom:var(--space-3);">Elige una bodega para ordenar:</p>';
+        html += '<div style="display:flex;flex-direction:column;gap:var(--space-2);">';
+        bodegas.forEach(function (b) {
+          html += '<div style="padding:var(--space-3);border:1px solid var(--glass-border);border-radius:var(--radius-md);display:flex;justify-content:space-between;align-items:center;">' +
+            '<div>' +
+              '<strong>' + esc(b.name) + '</strong>' +
+              '<div style="color:var(--color-text-muted);font-size:var(--text-caption);">' + esc(b.city || '') + ' · ' + esc(b.stock_hint) + '</div>' +
+            '</div>' +
+            '<div style="text-align:right;">' +
+              '<div class="price-range">$' + fmt(b.price) + '</div>' +
+              '<button style="margin-top:var(--space-1);padding:var(--space-1) var(--space-3);background:var(--gradient-accent);color:var(--btn-primary-text);border:none;border-radius:var(--radius-sm);font-size:var(--text-caption);cursor:pointer;" onclick="createOrderFor(null, ' + wiId + ', ' + b.id_bodega + ', \'' + esc(b.name).replace(/\'/g, '\\\'') + '\', ' + (b.price || 0) + ')">Ordenar</button>' +
+            '</div>' +
+          '</div>';
+        });
+        html += '</div>';
+        document.getElementById('partModalBody').innerHTML = html;
+      });
+    };
+
+    window.createOrderFor = function (partId, wiId, bodegaId, bodegaName, price) {
       var qty = prompt('Cantidad a ordenar para "' + bodegaName + '":', '1');
       if (!qty) return;
       qty = parseInt(qty);
@@ -265,12 +307,22 @@
 
       var notes = prompt('Notas para la bodega (opcional):', '') || '';
 
+      var item = { quantity: qty, unit_price: price };
+      if (partId) {
+        item.part_id = partId;
+      } else if (wiId) {
+        item.wi_id = wiId;
+      } else {
+        alert('Error: se requiere part_id o wi_id');
+        return;
+      }
+
       // Create PO draft
       apiFetch('/orders', {
         method: 'POST',
         body: JSON.stringify({
           bodega_id: bodegaId,
-          items: [{ part_id: partId, quantity: qty, unit_price: price }],
+          items: [item],
           delivery_method: 'pickup',
           buyer_notes: notes,
         }),
@@ -482,6 +534,10 @@
                   r.updated + ' actualizados';
         if (r.skipped > 0) msg += ', ' + r.skipped + ' omitidos';
         msg += '</span>';
+        if (r.oem_count !== undefined || r.seller_count !== undefined) {
+          msg += '<div style="margin-top:var(--space-2);font-size:var(--text-caption);color:var(--color-text-muted);">' +
+                 (r.oem_count || 0) + ' catálogo OEM · ' + (r.seller_count || 0) + ' seller listings</div>';
+        }
         if (r.errors && r.errors.length) {
           msg += '<div style="margin-top:var(--space-2);color:var(--color-text-muted);font-size:var(--text-caption);">';
           r.errors.slice(0, 5).forEach(function (e) {