Add gauge lab + maintenance asset references with enable/disable toggles

Dedicated assets.gaugelabreference and assets.maintenancereference columns
(distinct from assetnumber), surfaced on equipment. Add global per-identifier
enable/disable settings (gauge/maintenance/FQDN) read via a shared composable
and toggled in System Settings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/composables/identifierSettings.js

@@ -0,0 +1,36 @@
+// Global enable/disable flags for optional asset identifiers, read from the
+// settings table. Loaded once and shared across components. Defaults to
+// enabled when a flag is missing so a fresh install shows the identifiers.
+import { reactive } from 'vue'
+import { settingsApi } from '../api'
+
+const identifierflags = reactive({
+  gaugelabreference: true,
+  maintenancereference: true,
+  fqdn: true,
+  loaded: false
+})
+
+let inflight = null
+
+export function useIdentifierFlags() {
+  if (!identifierflags.loaded && !inflight) {
+    inflight = settingsApi.list()
+      .then(({ data }) => {
+        const map = {}
+        ;(data.data || []).forEach(s => { map[s.key] = s.value })
+        if ('identifier_gaugelabreference_enabled' in map) {
+          identifierflags.gaugelabreference = map.identifier_gaugelabreference_enabled !== false
+        }
+        if ('identifier_maintenancereference_enabled' in map) {
+          identifierflags.maintenancereference = map.identifier_maintenancereference_enabled !== false
+        }
+        if ('identifier_fqdn_enabled' in map) {
+          identifierflags.fqdn = map.identifier_fqdn_enabled !== false
+        }
+        identifierflags.loaded = true
+      })
+      .catch(() => { identifierflags.loaded = true })
+  }
+  return identifierflags
+}

frontend/src/views/settings/SystemSettings.vue

@@ -375,6 +375,60 @@
         </router-link>
       </div>
     </div>
+
+    <!-- Asset Identifiers Section -->
+    <div class="section-card">
+      <h2 class="section-title">Asset Identifiers</h2>
+
+      <div class="setting-group">
+        <p class="setting-description">
+          Enable or disable optional asset identifiers. When disabled, the identifier
+          is hidden from asset forms and detail pages across the system.
+        </p>
+
+        <div class="setting-row">
+          <label class="toggle-label">
+            <span>Gauge Lab Reference</span>
+            <button
+              class="toggle-btn"
+              :class="{ active: settings.identifier_gaugelabreference_enabled }"
+              @click="toggleSetting('identifier_gaugelabreference_enabled')"
+              :disabled="saving"
+            >
+              <span class="toggle-slider"></span>
+            </button>
+          </label>
+        </div>
+
+        <div class="setting-row">
+          <label class="toggle-label">
+            <span>Maintenance Reference</span>
+            <button
+              class="toggle-btn"
+              :class="{ active: settings.identifier_maintenancereference_enabled }"
+              @click="toggleSetting('identifier_maintenancereference_enabled')"
+              :disabled="saving"
+            >
+              <span class="toggle-slider"></span>
+            </button>
+          </label>
+        </div>
+
+        <div class="setting-row">
+          <label class="toggle-label">
+            <span>FQDN / Hostname</span>
+            <button
+              class="toggle-btn"
+              :class="{ active: settings.identifier_fqdn_enabled }"
+              @click="toggleSetting('identifier_fqdn_enabled')"
+              :disabled="saving"
+            >
+              <span class="toggle-slider"></span>
+            </button>
+          </label>
+        </div>
+      </div>
+    </div>
   </div>
 
   <div v-if="error" class="error-message">{{ error }}</div>
@@ -409,7 +463,11 @@ const settings = reactive({
   saml_acs_url: '',
   saml_allow_local_login: true,
   saml_auto_create_users: true,
-  saml_admin_group: ''
+  saml_admin_group: '',
+  // Asset identifiers
+  identifier_gaugelabreference_enabled: true,
+  identifier_maintenancereference_enabled: true,
+  identifier_fqdn_enabled: true
 })
 
 const loading = ref(true)