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>

shopdb/core/api/settings.py

@@ -17,6 +17,16 @@ SETTINGS_CACHE_TTL = 300  # 5 minutes
 # exposed in plaintext. Sending it back on update is treated as "unchanged".
 SECRET_MASK = '********'
 
+# Optional asset identifiers and the asset types they can be toggled on.
+# Drives per-type seed keys and the Settings matrix UI. The asset type names
+# match the AssetType.assettype values seeded by each plugin.
+IDENTIFIER_LABELS = {
+    'gaugelabreference': 'Gauge Lab Reference',
+    'maintenancereference': 'Maintenance Reference',
+    'fqdn': 'FQDN / hostname',
+}
+IDENTIFIER_ASSETTYPES = ['equipment', 'computer', 'printer', 'network_device']
+
 
 def _is_secret(key: str) -> bool:
     return 'password' in key or 'token' in key or 'secret' in key
@@ -155,29 +165,22 @@ def create_setting():
 @jwt_required()
 def seed_default_settings():
     """Seed default settings if they don't exist."""
-    defaults = [
-        # Asset identifier feature toggles (global, per identifier)
+    # Asset identifier feature toggles, per identifier AND per asset type.
+    # Key format: identifier_<name>_<assettype>_enabled (boolean). Admins pick
+    # which optional identifiers show on which asset types. See ADR-001.
+    identifierdefaults = [
         {
-            'key': 'identifier_gaugelabreference_enabled',
+            'key': f'identifier_{name}_{assettype}_enabled',
             'value': 'true',
             'valuetype': 'boolean',
             'category': 'identifiers',
-            'description': 'Show the Gauge Lab Reference identifier on assets'
-        },
-        {
-            'key': 'identifier_maintenancereference_enabled',
-            'value': 'true',
-            'valuetype': 'boolean',
-            'category': 'identifiers',
-            'description': 'Show the Maintenance Reference identifier on assets'
-        },
-        {
-            'key': 'identifier_fqdn_enabled',
-            'value': 'true',
-            'valuetype': 'boolean',
-            'category': 'identifiers',
-            'description': 'Show the FQDN / hostname identifier on assets'
-        },
+            'description': f'Show the {label} identifier on {assettype} assets',
+        }
+        for name, label in IDENTIFIER_LABELS.items()
+        for assettype in IDENTIFIER_ASSETTYPES
+    ]
+
+    defaults = identifierdefaults + [
         # Zabbix integration
         {
             'key': 'zabbix_enabled',