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/theme/vuetify-theme.js

@@ -0,0 +1,29 @@
+import { surfaces, text, action, semantic, accent } from './fabled-tokens.js'
+
+export const fabledCuratorTheme = {
+  dark: true,
+  colors: {
+    background:    surfaces.obsidian,
+    surface:       surfaces.iron,
+    'surface-bright': surfaces.slate,
+    'surface-light':  surfaces.pewter,
+
+    primary:    action.moss,
+    secondary:  action.bronze,
+    tertiary:   action.pewter,
+
+    'on-background': text.parchment,
+    'on-surface':    text.parchment,
+    'on-primary':    text.parchment,
+    'on-secondary':  text.parchment,
+
+    success: semantic.success,
+    warning: semantic.warning,
+    error:   semantic.error,
+    info:    semantic.info,
+
+    // Curator signature accent — used for nav-active state, wordmark, selection.
+    // Not on action buttons (see design-system.md "Accent usage rules").
+    accent:  accent.curator
+  }
+}