feat(devices): add console-only display name (console_name)

Lets staff set a friendly name for a device independent of whatever
name the end user gave it in the app. console_name is never shown to
app users and never synced from/to device_name; every display label
across search, equipment/helpdesk name resolution, device search, and
the Manage tab's issue linker now falls back through console_name ->
device_name -> serial rather than device_name alone.

Also includes an incidental one-line fix in devices/service.py: the
nested-struct deep-merge in update_device() was missing the newly
added device_health_settings key.

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

frontend/src/pages/bellcloud/devices/tabs/ManageTab.jsx

@@ -632,9 +632,9 @@ export default function ManageTab({ device, canEdit, deviceUsers: propUsers, use
         defaultType="issue"
         prefilledLinks={issueModal.entry
           ? undefined
-          : [{ entity_type: 'device', entity_id: id, display_name: device?.device_name || sn, locked: true }]
+          : [{ entity_type: 'device', entity_id: id, display_name: device?.console_name || device?.device_name || sn, locked: true }]
         }
-        knownEntities={id ? { [id]: device?.device_name || sn } : undefined}
+        knownEntities={id ? { [id]: device?.console_name || device?.device_name || sn } : undefined}
         onClose={() => setIssueModal({ open: false, entry: null })}
         onSaved={handleIssueSaved}
         onDelete={canEdit ? (entryId) => {

frontend/src/pages/bellcloud/users/UserDetail.jsx

@@ -820,7 +820,7 @@ export default function UserDetail() {
                     <option value="">Choose a device…</option>
                     {availableDevices.map((d) => (
                       <option key={d.id} value={d.id}>
-                        {d.device_name || 'Unnamed'} ({d.device_id || d.id})
+                        {d.console_name || d.device_name || 'Unnamed'} ({d.device_id || d.id})
                       </option>
                     ))}
                   </Select>
@@ -848,7 +848,7 @@ export default function UserDetail() {
                           onClick={() => navigate(`/devices/${device.id}`)}
                           style={{ background: 'none', border: 'none', cursor: 'pointer', padding: 0, fontSize: 'var(--font-size-sm)', fontWeight: 'var(--font-weight-semibold)', color: 'var(--color-text-accent)', textAlign: 'left', display: 'block', overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap', maxWidth: '160px' }}
                         >
-                          {device.device_name || 'Unnamed Device'}
+                          {device.console_name || device.device_name || 'Unnamed Device'}
                         </button>
                         <p style={{ fontFamily: 'var(--font-family-mono)', fontSize: 'var(--font-size-xs)', color: 'var(--color-text-muted)', marginTop: '2px' }}>
                           {device.device_id || device.id}

frontend/src/pages/bellcloud/users/UserListCardView.jsx

@@ -405,7 +405,7 @@ function LinkedDevicesModal({ userId, userName, open, onClose }) {
               <Icon name="device" size={14} color="var(--color-primary)" />
               <div style={{ flex: 1, minWidth: 0 }}>
                 <div style={{ fontWeight: 'var(--font-weight-medium)', color: 'var(--color-text-primary)', overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap' }}>
-                  {d.device_name || d.device_id || d.id}
+                  {d.console_name || d.device_name || d.device_id || d.id}
                 </div>
                 {d.device_id && (
                   <div style={{ color: 'var(--color-text-muted)', fontSize: 'var(--font-size-xs)', fontFamily: 'var(--font-family-mono)' }}>