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/components/menu/menu-item-model-viewer.tsx

@@ -0,0 +1,41 @@
+"use client";
+
+import "@google/model-viewer";
+import { resolveMediaUrl } from "@/lib/api/client";
+
+type MenuItemModelViewerProps = {
+  modelUrl: string;
+  posterUrl?: string | null;
+  alt: string;
+  className?: string;
+};
+
+export function MenuItemModelViewer({
+  modelUrl,
+  posterUrl,
+  alt,
+  className,
+}: MenuItemModelViewerProps) {
+  const src = resolveMediaUrl(modelUrl);
+  const poster = posterUrl ? resolveMediaUrl(posterUrl) : undefined;
+  if (!src) return null;
+
+  return (
+    // @ts-expect-error model-viewer is a custom element from @google/model-viewer
+    <model-viewer
+      src={src}
+      poster={poster}
+      alt={alt}
+      camera-controls
+      touch-action="pan-y"
+      auto-rotate
+      rotation-per-second="28deg"
+      interaction-prompt="none"
+      shadow-intensity="1"
+      exposure="1"
+      environment-image="neutral"
+      className={className}
+      style={{ width: "100%", height: "100%", minHeight: "min(72vh, 420px)" }}
+    />
+  );
+}