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/tailwind.config.ts

@@ -0,0 +1,49 @@
+import type { Config } from "tailwindcss";
+
+const config: Config = {
+  darkMode: ["class"],
+  content: ["./src/**/*.{ts,tsx}"],
+  theme: {
+    extend: {
+      colors: {
+        border: "hsl(var(--border))",
+        input: "hsl(var(--input))",
+        ring: "hsl(var(--ring))",
+        background: "hsl(var(--background))",
+        foreground: "hsl(var(--foreground))",
+        primary: {
+          DEFAULT: "hsl(var(--primary))",
+          foreground: "hsl(var(--primary-foreground))",
+        },
+        secondary: {
+          DEFAULT: "hsl(var(--secondary))",
+          foreground: "hsl(var(--secondary-foreground))",
+        },
+        muted: {
+          DEFAULT: "hsl(var(--muted))",
+          foreground: "hsl(var(--muted-foreground))",
+        },
+        accent: {
+          DEFAULT: "hsl(var(--accent))",
+          foreground: "hsl(var(--accent-foreground))",
+        },
+        destructive: {
+          DEFAULT: "hsl(var(--destructive))",
+          foreground: "hsl(var(--destructive-foreground))",
+        },
+        card: {
+          DEFAULT: "hsl(var(--card))",
+          foreground: "hsl(var(--card-foreground))",
+        },
+      },
+      borderRadius: {
+        lg: "var(--radius)",
+        md: "calc(var(--radius) - 2px)",
+        sm: "calc(var(--radius) - 4px)",
+      },
+    },
+  },
+  plugins: [],
+};
+
+export default config;