Add stage 5: list detail page with items UI and drag reorder

API: new PUT /api/lists/{id}/items/order takes the full ordered id set and
rewrites positions 0..n-1 in a transaction (422 unless the set matches the
list exactly). TodoItemRepository gains idsForList() and reorder().

Frontend: lists on the home page are now links to /lists/:id (ListView).
ListView shows the list title, a "M of N done" summary, and each item as a
drag handle + checkbox + inline-editable text (saved on blur) + delete
button, with a create-item form at the bottom. Drag-and-drop uses
vuedraggable; on drop the whole order is persisted via the new endpoint and
the response replaces local state, with a resync-on-error fallback. New
items store; items store is also reset on logout.

Tests: reorder happy path, incomplete-set rejection, owner scoping. Backend
suite: 23 passing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/router/index.ts

@@ -10,6 +10,12 @@ const router = createRouter({
       component: () => import('../views/HomeView.vue'),
       meta: { requiresAuth: true },
     },
+    {
+      path: '/lists/:id(\\d+)',
+      name: 'list',
+      component: () => import('../views/ListView.vue'),
+      meta: { requiresAuth: true },
+    },
     {
       path: '/login',
       name: 'login',