Add todo list with kanban board view

- todos table with title, description, status (todo/in_progress/done),
  priority (urgent/high/medium/low), optional device link, due date
- List view: sorted by priority, inline edit, click-to-advance status
  circle (empty → blue dot → green check), edit/delete actions
- Kanban board view: three columns, move buttons between statuses,
  priority badges, device links, due dates
- Toggle between List and Board views via URL param
- Optional link to a device for repair-related todos
- Sidebar nav item added

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: '/todos',
+			label: 'Todos',
+			icon: 'M9 12l2 2 4-4m6 2a9 9 0 11-18 0 9 9 0 0118 0z'
+		},
 		{
 			href: '/checklists',
 			label: 'Checklists',