Add a persistent left sidebar to the signed-in layout

App.vue now renders a left AppSidebar beside the routed view for any
requiresAuth page, staying mounted as you move between the dashboard and
projects. The sidebar has a Dashboard link (icon), a divider, the project list
(each an icon link, current page highlighted via RouterLink active-class), and a
compact new-project form that jumps to the created project.

- New /dashboard route + DashboardView ("under construction"); / and unknown
  paths redirect there. HomeView removed -- its project list and form moved into
  the sidebar.
- <RouterView :key="route.path"> so navigating project -> project via the
  sidebar remounts and reloads instead of reusing the instance.
- Signed-out routes (login/register/verify-email) render without the sidebar.

Icons are inline SVG -- no new dependency.

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

web/src/router/index.ts

@@ -4,10 +4,11 @@ import { useAuthStore } from '../stores/auth'
 const router = createRouter({
   history: createWebHistory(import.meta.env.BASE_URL),
   routes: [
+    { path: '/', redirect: { name: 'dashboard' } },
     {
-      path: '/',
-      name: 'home',
-      component: () => import('../views/HomeView.vue'),
+      path: '/dashboard',
+      name: 'dashboard',
+      component: () => import('../views/DashboardView.vue'),
       meta: { requiresAuth: true },
     },
     {
@@ -40,22 +41,24 @@ const router = createRouter({
       component: () => import('../views/RegisterView.vue'),
       meta: { guestOnly: true },
     },
-    { path: '/:pathMatch(.*)*', redirect: { name: 'home' } },
+    { path: '/:pathMatch(.*)*', redirect: { name: 'dashboard' } },
   ],
 })
 
+const DEFAULT_PATHS = new Set(['/', '/dashboard'])
+
 router.beforeEach((to) => {
   const auth = useAuthStore()
 
   if (to.meta.requiresAuth && !auth.isAuthenticated) {
     return {
       name: 'login',
-      query: to.fullPath === '/' ? {} : { redirect: to.fullPath },
+      query: DEFAULT_PATHS.has(to.path) ? {} : { redirect: to.fullPath },
     }
   }
 
   if (to.meta.guestOnly && auth.isAuthenticated) {
-    return { name: 'home' }
+    return { name: 'dashboard' }
   }
 })