feat(dashboard): Next.js 16 merchant panel with offline POS and PWA

Complete merchant dashboard upgrade:

Next.js 16 compatibility:
- Fix params/searchParams typed as Promise<{}> throughout App Router
- Replace middleware.ts with proxy.ts (Next.js 16 convention)
- Remove unused @ts-expect-error directives caught by stricter TS
- Cast dynamic next-intl t() keys to fix TranslateArgs type errors

Offline POS:
- IndexedDB queue (meezi_pos_offline) for orders created while offline
- Zustand sync store tracking queueCount, isSyncing, isOnline
- useOfflineSync hook: auto-syncs on reconnect/visibility-change
- SyncStatusIndicator chip in topbar (amber=offline, blue=syncing)
- submitOrderToApi falls back to local order on network failure
- Local orders skip payment flow; sync on reconnect

PWA (installable):
- @ducanh2912/next-pwa with Workbox runtime caching rules
- Web App Manifest (manifest.ts) — RTL/Farsi, theme #0F6E56
- PWA icons: 192px, 512px, maskable 512px
- next.config.ts replaces next.config.mjs

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

web/dashboard/src/lib/menu-display.ts

@@ -0,0 +1,58 @@
+/** Localized menu label: primary name for locale + English line for international guests. */
+
+export type MenuNameFields = {
+  name: string;
+  nameEn?: string | null;
+  nameAr?: string | null;
+};
+
+export function getMenuPrimaryName(
+  item: MenuNameFields,
+  locale: string
+): string {
+  const en = item.nameEn?.trim();
+  const ar = item.nameAr?.trim();
+  const fa = item.name.trim();
+
+  if (locale === "en") return en || fa;
+  if (locale === "ar") return ar || fa;
+  return fa;
+}
+
+/** English subtitle when primary is fa/ar (helps staff and international customers). */
+export function getMenuEnglishSubtitle(
+  item: MenuNameFields,
+  locale: string
+): string | undefined {
+  const en = item.nameEn?.trim();
+  if (!en) return undefined;
+
+  const primary = getMenuPrimaryName(item, locale);
+  if (primary === en) return undefined;
+
+  if (locale === "en") return undefined;
+
+  return en;
+}
+
+/** Case-insensitive match for POS / menu search (fa, en, ar, description). */
+export function menuItemMatchesSearch(
+  item: MenuNameFields & { description?: string | null },
+  query: string,
+  locale: string
+): boolean {
+  const q = query.trim().toLowerCase();
+  if (!q) return true;
+  const haystack = [
+    item.name,
+    item.nameEn,
+    item.nameAr,
+    item.description,
+    getMenuPrimaryName(item, locale),
+    getMenuEnglishSubtitle(item, locale),
+  ]
+    .filter((s): s is string => typeof s === "string" && s.length > 0)
+    .join(" ")
+    .toLowerCase();
+  return haystack.includes(q);
+}