feat(workshop): make brand/model required, plate optional, remove VIN

- create_vehicle endpoints now require make and model; plate is optional; VIN is no longer stored.

- Updated new-vehicle modal: removed VIN field, plate is optional, brand/model marked required.

pos/templates/workshop.html

@@ -15,7 +15,7 @@
   <meta name="theme-color" content="#F5A623" />
   <link rel="shortcut icon" type="image/png" href="/pos/static/pwa/icon-192.png" />
 
-  <link rel="stylesheet" href="/pos/static/css/workshop.css?v=41">
+  <link rel="stylesheet" href="/pos/static/css/workshop.css?v=42">
   <style>
     .so-notes-grid { display: grid; grid-template-columns: 120px 1fr; gap: var(--space-2); align-items: start; }
     .so-notes-grid .form-label { margin: 0; padding-top: var(--space-2); }
@@ -348,19 +348,15 @@
     <div class="modal__body">
       <form class="form-grid" id="newVehicleForm" onsubmit="return false;">
         <div class="form-field">
-          <label class="form-label" for="nvPlate">Placa *</label>
-          <input class="form-input" id="nvPlate" placeholder="Ej. ABC-123" />
+          <label class="form-label" for="nvPlate">Placa</label>
+          <input class="form-input" id="nvPlate" placeholder="Ej. ABC-123 (opcional)" />
         </div>
         <div class="form-field">
-          <label class="form-label" for="nvVIN">VIN</label>
-          <input class="form-input" id="nvVIN" placeholder="N&uacute;mero de serie" />
-        </div>
-        <div class="form-field">
-          <label class="form-label" for="nvMake">Marca</label>
+          <label class="form-label" for="nvMake">Marca *</label>
           <input class="form-input" id="nvMake" placeholder="Ej. Nissan" />
         </div>
         <div class="form-field">
-          <label class="form-label" for="nvModel">Modelo</label>
+          <label class="form-label" for="nvModel">Modelo *</label>
           <input class="form-input" id="nvModel" placeholder="Ej. Versa" />
         </div>
         <div class="form-field">
@@ -487,7 +483,7 @@
 <script src="/pos/static/js/pos-utils.js?v=33" defer></script>
 <script src="/pos/static/js/sidebar.js?v=36" defer></script>
 <script src="/pos/static/js/offline-banner.js" defer></script>
-<script src="/pos/static/js/workshop.js?v=41" defer></script>
+<script src="/pos/static/js/workshop.js?v=42" defer></script>
 <script>if('serviceWorker' in navigator){navigator.serviceWorker.register('/pos/sw.js',{scope:'/pos/'});}</script>
 <script src="/pos/static/js/pwa-install.js" defer></script>
 <script src="/pos/static/js/chat.js" defer></script>