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/src/db/database.js

@@ -0,0 +1,43 @@
+import SQLiteESMFactory from '@journeyapps/wa-sqlite/dist/wa-sqlite-async.mjs'
+import { IDBBatchAtomicVFS } from '@journeyapps/wa-sqlite/src/examples/IDBBatchAtomicVFS.js'
+import * as SQLite from '@journeyapps/wa-sqlite'
+import { SCHEMA_SQL } from './schema.js'
+
+let db = null
+let sqlite3 = null
+const tableListeners = new Map()
+
+export async function initDatabase() {
+  if (db) return db
+  const module = await SQLiteESMFactory()
+  sqlite3 = SQLite.Factory(module)
+  const vfs = await IDBBatchAtomicVFS.create('roaauto', module)
+  sqlite3.vfs_register(vfs, true)
+  db = await sqlite3.open_v2('roaauto.db',
+    SQLite.SQLITE_OPEN_READWRITE | SQLite.SQLITE_OPEN_CREATE, 'roaauto')
+  for (const sql of SCHEMA_SQL.split(';').filter(s => s.trim())) {
+    await sqlite3.exec(db, sql)
+  }
+  return db
+}
+
+export function notifyTableChanged(table) {
+  tableListeners.get(table)?.forEach(cb => cb())
+}
+
+export function onTableChange(table, cb) {
+  if (!tableListeners.has(table)) tableListeners.set(table, new Set())
+  tableListeners.get(table).add(cb)
+  return () => tableListeners.get(table).delete(cb)
+}
+
+export async function execSQL(sql, params = []) {
+  if (!db) throw new Error('DB not initialized')
+  const results = []
+  await sqlite3.exec(db, sql, (row, cols) => {
+    const obj = {}
+    cols.forEach((c, i) => { obj[c] = row[i] })
+    results.push(obj)
+  })
+  return results
+}