displays: single display type with IP-driven role (dashboard/lobby/kiosk)

One 'display' image resolves what it shows from its own IP, like the existing
visitor-location BU mapping. Extend DashboardDefault with displayrole
(dashboard|lobby|partskiosk; migration 7d28, businessunitid now nullable since
only the dashboard role needs one) + a role->path map. New unauthenticated
GET /api/dashboarddefaults/display-role returns {role, path, businessunitid}
for the caller IP. Settings UI gains a Display selector, showing the business
unit only for the dashboard role.

frontend/src/views/settings/DashboardDefaultsList.vue

@@ -6,9 +6,9 @@
     </div>
 
     <p class="setting-description">
-      Map a kiosk/lobby display's IP address to the business unit it should show.
-      The shopfloor dashboard auto-selects this business unit by the display's IP
-      when none is chosen.
+      Map a display PC's IP address to what it should show: the shopfloor
+      dashboard (and which business unit), the lobby slideshow, or the 3D parts
+      kiosk. A single "display" image resolves its role from its own IP.
     </p>
 
     <div class="card">
@@ -20,6 +20,7 @@
             <thead>
               <tr>
                 <th>IP Address</th>
+                <th>Display</th>
                 <th>Business Unit</th>
                 <th>Description</th>
                 <th>Actions</th>
@@ -28,6 +29,7 @@
             <tbody>
               <tr v-for="d in items" :key="d.dashboarddefaultid">
                 <td class="mono">{{ d.ipaddress }}</td>
+                <td>{{ roleLabel(d.displayrole) }}</td>
                 <td>{{ d.businessunit || '-' }}</td>
                 <td class="cell-truncate" :title="d.description">{{ d.description || '-' }}</td>
                 <td class="actions">
@@ -36,7 +38,7 @@
                 </td>
               </tr>
               <tr v-if="items.length === 0">
-                <td colspan="4" style="text-align: center; color: var(--text-light);">
+                <td colspan="5" style="text-align: center; color: var(--text-light);">
                   No mappings yet
                 </td>
               </tr>
@@ -60,8 +62,15 @@
                      placeholder="e.g., 10.20.30.40" required />
             </div>
             <div class="form-group">
+              <label for="displayrole">Display *</label>
+              <select id="displayrole" v-model="form.displayrole" class="form-control" required>
+                <option v-for="r in roleOptions" :key="r.value" :value="r.value">{{ r.label }}</option>
+              </select>
+            </div>
+            <div class="form-group" v-if="form.displayrole === 'dashboard'">
               <label for="businessunitid">Business Unit *</label>
-              <select id="businessunitid" v-model="form.businessunitid" class="form-control" required>
+              <select id="businessunitid" v-model="form.businessunitid" class="form-control"
+                      :required="form.displayrole === 'dashboard'">
                 <option value="">Select business unit...</option>
                 <option v-for="bu in businessUnits" :key="bu.businessunitid" :value="bu.businessunitid">
                   {{ bu.businessunit }}
@@ -108,6 +117,15 @@ import { useToast } from '../../composables/toast'
 import { apiError } from '../../utils/apiError'
 const toast = useToast()
 
+const roleOptions = [
+  { value: 'dashboard', label: 'Shopfloor Dashboard' },
+  { value: 'lobby', label: 'Lobby Slideshow' },
+  { value: 'partskiosk', label: '3D Parts Kiosk' },
+]
+function roleLabel(value) {
+  return roleOptions.find(r => r.value === value)?.label || value
+}
+
 const items = ref([])
 const businessUnits = ref([])
 const loading = ref(true)
@@ -120,7 +138,7 @@ const error = ref('')
 const showDeleteModal = ref(false)
 const toDelete = ref(null)
 
-const form = ref({ ipaddress: '', businessunitid: '', description: '' })
+const form = ref({ ipaddress: '', displayrole: 'dashboard', businessunitid: '', description: '' })
 
 onMounted(async () => {
   try {
@@ -148,9 +166,10 @@ function openModal(item = null) {
   editing.value = item
   form.value = item ? {
     ipaddress: item.ipaddress || '',
+    displayrole: item.displayrole || 'dashboard',
     businessunitid: item.businessunitid || '',
     description: item.description || ''
-  } : { ipaddress: '', businessunitid: '', description: '' }
+  } : { ipaddress: '', displayrole: 'dashboard', businessunitid: '', description: '' }
   error.value = ''
   showModal.value = true
 }