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/network/NetworkDeviceDetail.vue

@@ -2,7 +2,8 @@
   <div class="detail-page" v-if="device">
     <div class="hero-card">
       <div class="hero-image">
-        <div class="device-icon">
+        <img v-if="device.networkdevice?.imageurl" :src="device.networkdevice.imageurl" alt="Model photo" />
+        <div class="device-icon" v-else>
           <span class="icon"><component :is="getDeviceIcon()" :size="24" /></span>
         </div>
       </div>