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/next.config.ts

@@ -0,0 +1,72 @@
+import type { NextConfig } from "next";
+import createNextIntlPlugin from "next-intl/plugin";
+import withPWAInit from "@ducanh2912/next-pwa";
+
+const withNextIntl = createNextIntlPlugin("./src/i18n/request.ts");
+
+const withPWA = withPWAInit({
+  dest: "public",
+  cacheOnFrontEndNav: true,
+  aggressiveFrontEndNavCaching: true,
+  reloadOnOnline: true,
+  disable: process.env.NODE_ENV === "development",
+  workboxOptions: {
+    disableDevLogs: true,
+    runtimeCaching: [
+      // App shell: cache-first, very long TTL
+      {
+        urlPattern: /\/_next\/static\//,
+        handler: "CacheFirst",
+        options: {
+          cacheName: "static-assets",
+          expiration: { maxEntries: 200, maxAgeSeconds: 30 * 24 * 60 * 60 },
+        },
+      },
+      // API: NetworkFirst — show cached data when offline
+      {
+        urlPattern: /\/api\//,
+        handler: "NetworkFirst",
+        options: {
+          cacheName: "api-data",
+          networkTimeoutSeconds: 5,
+          expiration: { maxEntries: 300, maxAgeSeconds: 10 * 60 },
+        },
+      },
+      // Menu images & media
+      {
+        urlPattern: /\.(?:png|jpg|jpeg|svg|gif|webp|ico)$/,
+        handler: "StaleWhileRevalidate",
+        options: {
+          cacheName: "media-cache",
+          expiration: { maxEntries: 300, maxAgeSeconds: 7 * 24 * 60 * 60 },
+        },
+      },
+    ],
+  },
+});
+
+const adminWebOrigin =
+  process.env.ADMIN_WEB_ORIGIN ?? "http://localhost:3102";
+
+const nextConfig: NextConfig = {
+  output: "standalone",
+  experimental: {
+    optimizePackageImports: ["recharts", "lucide-react"],
+  },
+  async redirects() {
+    return [
+      {
+        source: "/:locale(fa|ar|en)/admin",
+        destination: `${adminWebOrigin}/:locale/admin`,
+        permanent: false,
+      },
+      {
+        source: "/:locale(fa|ar|en)/admin/:path*",
+        destination: `${adminWebOrigin}/:locale/admin/:path*`,
+        permanent: false,
+      },
+    ];
+  },
+};
+
+export default withPWA(withNextIntl(nextConfig));