Render vendor-model photos on asset detail heroes

Computer and Printer payloads now surface the linked model imageurl the
way machines already did, and the machine/PC/printer detail heroes
render the photo when present (network devices and measuring tools
have no model link, so nothing to surface). Absent images render
nothing rather than a broken icon.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/views/printers/PrinterDetail.vue

@@ -16,6 +16,9 @@
     <template v-else-if="printer">
       <!-- Hero Section -->
       <div class="hero-card">
+        <div class="hero-image" v-if="printer.printer?.imageurl">
+          <img :src="printer.printer.imageurl" :alt="printer.printer.modelname || 'Model photo'" />
+        </div>
         <div class="hero-content">
           <div class="hero-title">
             <h1>{{ displayTitle }}</h1>