Make gauge/maintenance identifiers per-asset-type and extend to all types

Optional asset identifiers (gauge lab reference, maintenance reference, FQDN)
were global per-identifier and only surfaced on equipment. Now they are
toggleable per asset type and rendered on every asset type.

- settings: replace 3 global identifier toggles with a per-type matrix. New
  keys identifier_<name>_<assettype>_enabled (3 identifiers x 4 types).
  IDENTIFIER_LABELS / IDENTIFIER_ASSETTYPES constants drive the seed (API seed
  and CLI seed settings).
- composable: identifierSettings now exposes isEnabled(name, assettype),
  per-type flag winning over the legacy global key, defaulting on.
- backend writes: computers, network, printers asset create + update now
  accept gaugelabreference and maintenancereference (equipment already did).
  Reads already flowed through Asset.to_dict.
- frontend: Settings page renders an identifier x asset-type toggle matrix.
  Equipment, PC, printer, network forms and detail pages show gauge/maintenance
  (and FQDN where applicable) gated by isEnabled(name, type).

Legacy global identifier_<name>_enabled keys are still honored as a fallback
for older installs. SystemSettings toggles upsert (create on 404) so a deploy
that has not re-seeded still works on first toggle.

144 tests pass, naming/style check green, frontend builds. Verified live:
matrix renders, PC form shows the fields, PUT persists gauge/maintenance on a
PC and reads back.

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

frontend/src/views/network/NetworkDeviceDetail.vue

@@ -111,6 +111,14 @@
               <span class="info-label">Serial Number</span>
               <span class="info-value mono">{{ device.serialnumber || '-' }}</span>
             </div>
+            <div class="info-row" v-if="isEnabled('gaugelabreference', 'network_device') && device.gaugelabreference">
+              <span class="info-label">Gauge Lab Reference</span>
+              <span class="info-value mono">{{ device.gaugelabreference }}</span>
+            </div>
+            <div class="info-row" v-if="isEnabled('maintenancereference', 'network_device') && device.maintenancereference">
+              <span class="info-label">Maintenance Reference</span>
+              <span class="info-value mono">{{ device.maintenancereference }}</span>
+            </div>
             <div class="info-row">
               <span class="info-label">Vendor</span>
               <span class="info-value">{{ device.networkdevice?.vendorname || '-' }}</span>
@@ -181,6 +189,9 @@ import { Network, Router, Shield, Wifi, Camera, Server, Server as Rack, Globe }
 import { useAuthStore } from '../../stores/auth'
 import { networkApi } from '../../api'
 import AssetRelationships from '../../components/AssetRelationships.vue'
+import { useIdentifierFlags } from '../../composables/identifierSettings'
+
+const { isEnabled } = useIdentifierFlags()
 
 const route = useRoute()
 const router = useRouter()

frontend/src/views/network/NetworkDeviceForm.vue

@@ -54,6 +54,27 @@
             </div>
           </div>
 
+          <div class="form-row" v-if="isEnabled('gaugelabreference', 'network_device') || isEnabled('maintenancereference', 'network_device')">
+            <div class="form-group" v-if="isEnabled('gaugelabreference', 'network_device')">
+              <label for="gaugelabreference">Gauge Lab Reference</label>
+              <input
+                id="gaugelabreference"
+                v-model="form.gaugelabreference"
+                type="text"
+                class="form-control"
+              />
+            </div>
+            <div class="form-group" v-if="isEnabled('maintenancereference', 'network_device')">
+              <label for="maintenancereference">Maintenance Reference</label>
+              <input
+                id="maintenancereference"
+                v-model="form.maintenancereference"
+                type="text"
+                class="form-control"
+              />
+            </div>
+          </div>
+
           <div class="form-row">
             <div class="form-group">
               <label for="locationid">Location</label>
@@ -229,6 +250,9 @@ import {
   assetsApi,
   businessunitsApi
 } from '../../api'
+import { useIdentifierFlags } from '../../composables/identifierSettings'
+
+const { isEnabled } = useIdentifierFlags()
 
 const route = useRoute()
 const router = useRouter()
@@ -240,6 +264,8 @@ const form = ref({
   assetnumber: '',
   name: '',
   serialnumber: '',
+  gaugelabreference: '',
+  maintenancereference: '',
   statusid: '',
   locationid: '',
   businessunitid: '',
@@ -332,6 +358,8 @@ async function loadDevice() {
     form.value.assetnumber = data.assetnumber || ''
     form.value.name = data.name || ''
     form.value.serialnumber = data.serialnumber || ''
+    form.value.gaugelabreference = data.gaugelabreference || ''
+    form.value.maintenancereference = data.maintenancereference || ''
     form.value.statusid = data.statusid || ''
     form.value.locationid = data.locationid || ''
     form.value.businessunitid = data.businessunitid || ''
@@ -365,6 +393,8 @@ async function submitForm() {
       assetnumber: form.value.assetnumber,
       name: form.value.name || null,
       serialnumber: form.value.serialnumber || null,
+      gaugelabreference: form.value.gaugelabreference || null,
+      maintenancereference: form.value.maintenancereference || null,
       statusid: form.value.statusid || null,
       locationid: form.value.locationid || null,
       businessunitid: form.value.businessunitid || null,