Rework device type view to group by deviceType tag

- /api/devices now groups hosts by deviceType tag instead of host group;
  hosts without the tag are skipped
- /api/detail device lookup filters by deviceType tag instead of groupid
- getTag() is now case-insensitive on the tag name
- Removed selectHostGroups from fetchKFCData (no longer needed)
- Frontend: hex id and Zabbix deep-link use deviceType instead of groupid
- Smaller hex label (1.2rem) for device type view via hex-item--device class
- Skip DOM re-render on auto-refresh when data is unchanged (lastDataKey diff)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/style.css

@@ -317,6 +317,11 @@ header {
 
 .hex-item:active { transform: scale(0.97); }
 
+.hex-item--device .hex-label {
+  font-size: 1.2rem;
+  font-weight: 700;
+}
+
 .hex-label {
   font-size: 1.8rem;
   font-weight: 800;