feat(frontend): Vue 3 + wa-sqlite + sync engine + auth + layouts

- package.json with Vue 3, Pinia, vue-router, wa-sqlite, Tailwind CSS 4, Vite
- wa-sqlite database layer with IDBBatchAtomicVFS (offline-first)
- Full schema mirroring backend tables (vehicles, orders, invoices, etc.)
- SyncEngine: fullSync, incrementalSync, pushQueue for offline queue
- Auth store with JWT parsing, login/register, plan tier detection
- Router with all routes and auth navigation guards
- AppLayout (sidebar desktop / bottom nav mobile) + AuthLayout
- Login/Register views connected to API contract
- SyncIndicator component (online/offline status)
- Reactive SQL query composable (useSqlQuery)
- Placeholder views for dashboard, orders, vehicles, appointments, catalog, settings

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

frontend/vite.config.js

@@ -0,0 +1,21 @@
+import { defineConfig } from 'vite'
+import vue from '@vitejs/plugin-vue'
+import tailwindcss from '@tailwindcss/vite'
+
+export default defineConfig({
+  plugins: [
+    vue(),
+    tailwindcss(),
+  ],
+  server: {
+    proxy: {
+      '/api': {
+        target: 'http://localhost:8000',
+        changeOrigin: true,
+      },
+    },
+  },
+  optimizeDeps: {
+    exclude: ['@journeyapps/wa-sqlite'],
+  },
+})