feat: scaffold Vue 3 + Vuetify + Pinia frontend themed to FabledDesignSystem

Curator signature accent (#A87338, aged amber) is baked into
fabled-tokens.js. Vuetify theme consumes the same tokens module the rest
of the SPA does, so updating design system tokens propagates throughout.
Vite dev server proxies /api and /ws to the Quart backend.

App.vue references AppShell (lands in Task 9) and main.js references
router.js (lands in Task 9) — these are intentionally split so Task 8 is
the framework scaffold and Task 9 is the navigation/shell content.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/main.js

@@ -0,0 +1,26 @@
+import { createApp } from 'vue'
+import { createPinia } from 'pinia'
+import { createVuetify } from 'vuetify'
+import 'vuetify/styles'
+import '@mdi/font/css/materialdesignicons.css'
+
+import App from './App.vue'
+import router from './router.js'
+import { fabledCuratorTheme } from './theme/vuetify-theme.js'
+
+const vuetify = createVuetify({
+  theme: {
+    defaultTheme: 'fabledCurator',
+    themes: { fabledCurator: fabledCuratorTheme }
+  },
+  defaults: {
+    // FabledDesignSystem: pill shape for buttons
+    VBtn: { rounded: 'pill' }
+  }
+})
+
+createApp(App)
+  .use(createPinia())
+  .use(router)
+  .use(vuetify)
+  .mount('#app')