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/e2e/api-health.spec.ts

@@ -0,0 +1,28 @@
+import { test, expect } from "@playwright/test";
+
+const apiURL = process.env.PLAYWRIGHT_API_URL ?? "http://localhost:5080";
+
+test.describe("API health", () => {
+  test("GET /health returns 200", async ({ request }) => {
+    const res = await request.get(`${apiURL}/health`);
+    expect(res.ok()).toBeTruthy();
+    const body = await res.json();
+    expect(body.status).toBe("healthy");
+  });
+
+  test("GET /api/public/security-config", async ({ request }) => {
+    const res = await request.get(`${apiURL}/api/public/security-config`);
+    expect(res.ok()).toBeTruthy();
+    const json = await res.json();
+    expect(json.success).toBe(true);
+    expect(json.data).toBeDefined();
+  });
+
+  test("GET /api/public/discover returns list", async ({ request }) => {
+    const res = await request.get(`${apiURL}/api/public/discover?city=تهران`);
+    expect(res.ok()).toBeTruthy();
+    const json = await res.json();
+    expect(json.success).toBe(true);
+    expect(Array.isArray(json.data)).toBe(true);
+  });
+});