Add checklist templates with import into devices

- checklist_templates and template_items tables for reusable checklists
- /checklists page: create/edit/delete templates with ordered items
- "Import" button on device detail imports a template as a new checklist
  with all items copied (unchecked)
- Sidebar nav item for Checklists between Locations and Gallery

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/components/layout/Sidebar.svelte

@@ -37,6 +37,11 @@
 			label: 'Locations',
 			icon: 'M17.657 16.657L13.414 20.9a1.998 1.998 0 01-2.827 0l-4.244-4.243a8 8 0 1111.314 0z M15 11a3 3 0 11-6 0 3 3 0 016 0z'
 		},
+		{
+			href: '/checklists',
+			label: 'Checklists',
+			icon: 'M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2m-6 9l2 2 4-4'
+		},
 		{
 			href: '/gallery',
 			label: 'Gallery',