feat: selector de region en catalogo publico (MX/USA/CA, Europa, Asia, Todos)

Filtra marcas por mercado regional. 4 opciones:
- Mexico/USA/Canada (36 marcas)
- Europa (27 marcas)
- Asia (15 marcas)
- Todos (546 marcas)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dashboard/catalog-public.js

@@ -16,10 +16,22 @@
     engine: null,          // {id_mye, name, trim}
     category: null,        // {id, name}
     group: null,           // {id, name}
+    region: 'north-america',
     page: 1,
     totalPages: 1,
   };
 
+  // ── Region selector (global) ──
+  window.setRegion = function (region) {
+    state.region = region;
+    document.querySelectorAll('.region-btn').forEach(function (b) {
+      b.classList.toggle('is-active', b.dataset.region === region);
+    });
+    // Reload brands with new region
+    state.brand = state.model = state.year = state.engine = state.category = state.group = null;
+    loadBrands();
+  };
+
   var API = '/api/catalog';
   var content = document.getElementById('content');
   var breadcrumbEl = document.getElementById('breadcrumb');
@@ -170,7 +182,7 @@
     state.level = 'brands';
     renderBreadcrumb();
     content.innerHTML = '<div class="loading">Cargando marcas...</div>';
-    fetch(API + '/brands')
+    fetch(API + '/brands?region=' + (state.region || 'north-america'))
       .then(function (r) { return r.json(); })
       .then(function (brands) {
         var html = '<h2>Selecciona una Marca</h2><div class="nav-grid">';