Asset-side printer save, status CRUD, real printer types, network fix

- Printers save through the asset blueprint (PUT /printers) instead of the
  legacy machines API; restrict supply-model picker to printer models.
- Asset statuses get full CRUD (PUT/DELETE with in-use guard); canonical set.
- Printer types reseeded to a real classification set + list filter.
- Equipment accepts gauge/maintenance references.
- Fix network list emitting network_device instead of networkdevice (View 404).

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

shopdb/config.py

@@ -53,6 +53,7 @@ class Config:
 
     LOG_LEVEL = os.environ.get('LOG_LEVEL', 'INFO')
 
+    ZABBIX_ENABLED = os.environ.get('ZABBIX_ENABLED', 'false').lower() == 'true'
     ZABBIX_URL = os.environ.get('ZABBIX_URL', '')
     ZABBIX_TOKEN = os.environ.get('ZABBIX_TOKEN', '')