feat(portal): strip Vuexy demo content and create clean portal shell

Remove all demo pages, dialogs, sidebar navigation, and layout components.
Create minimal top-bar portal layout with auth-aware navigation, placeholder
pages for volunteer registration, dashboard, shifts, profile, artist advance,
and login. Add Pinia auth store, axios with Sanctum support, and router guards.

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

apps/portal/env.d.ts

@@ -1,12 +1,11 @@
 import 'vue-router'
 declare module 'vue-router' {
   interface RouteMeta {
-    action?: string
-    subject?: string
     layoutWrapperClasses?: string
     navActiveLink?: RouteLocationRaw
-    layout?: 'blank' | 'default'
-    unauthenticatedOnly?: boolean
+    layout?: 'blank' | 'default' | 'portal'
+    requiresAuth?: boolean
+    requiresToken?: boolean
     public?: boolean
   }
 }