feat(story-1.2): Vue 3 SPA scaffold, base component library, User entity, SpaController

Frontend:
- Vue 3 + Vite + TypeScript strict in frontend/; builds to public/build/
- Vue Router (hash-history, requiresAuth guard → /login) and Pinia
- Global SCSS design tokens with 6 full themes (Warm Craft, Playful Pop, Sage & Cream, Dusty Mauve, Ocean Dusk, Honey & Slate)
- Base components: BaseButton (5 variants), BaseInput (floating label, error state),
  BaseBottomSheet (slide-up, focus trap, tap-outside dismiss), BaseCard, BaseChip,
  BaseToast (2.5s auto-dismiss, aria-live polite), BottomNav (4 tabs, hides at 960px)
- Type stubs for all API shapes: User, Device, Image, StickerLayer, RenderedAsset, Token

Backend:
- SpaController catch-all serves public/build/index.html; excludes api/setup/token/login/register
- User entity (email+password+roles+theme); UserRepository with PasswordUpgrader
- SecurityController with /login, /logout, /register stubs; Twig login form
- security.yaml: form_login firewall, remember_me, role_hierarchy, access_control
- Migration: create user table

Verified: npm run build succeeds, GET / → 302 /login (unauthenticated)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "frontend",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vue-tsc -b && vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "pinia": "^3.0.4",
+    "sass": "^1.99.0",
+    "vue": "^3.5.32",
+    "vue-router": "^4.6.4"
+  },
+  "devDependencies": {
+    "@types/node": "^24.12.2",
+    "@vitejs/plugin-vue": "^6.0.6",
+    "@vue/tsconfig": "^0.9.1",
+    "typescript": "~6.0.2",
+    "vite": "^8.0.10",
+    "vue-tsc": "^3.2.7"
+  }
+}