feat(web): responsive app shell + tab navigation

src/app/(app)/AppNav.tsx

@@ -0,0 +1,19 @@
+"use client";
+
+import { usePathname } from "next/navigation";
+import { TabBar, type TabKey } from "@/ds";
+
+const TAB_ORDER: TabKey[] = ["home", "accounting", "planner", "assets", "profile"];
+
+function activeTabFor(pathname: string | null): TabKey {
+  const match = TAB_ORDER.find((key) => pathname?.startsWith(`/${key}`));
+  return match ?? "home";
+}
+
+/** Client-only sliver of the shell: reads the current route so the layout
+ * (a server component) can stay server-rendered while `TabBar` still knows
+ * which tab is active. */
+export function AppNav() {
+  const pathname = usePathname();
+  return <TabBar active={activeTabFor(pathname)} />;
+}

src/app/(app)/home/page.tsx

@@ -0,0 +1,6 @@
+import { t } from "@/i18n/common";
+
+// Placeholder — Task 9 replaces this with the real dashboard.
+export default function HomePage() {
+  return <h1 style={{ fontWeight: 700 }}>{t.tabs.home}</h1>;
+}

src/app/(app)/layout.tsx

@@ -0,0 +1,20 @@
+import type { ReactNode } from "react";
+import { AppQueryProvider } from "@/api/queryClient";
+import { AppNav } from "./AppNav";
+
+/** Shell for every authed route (guarded by middleware). Bottom tab bar on
+ * mobile, left sidebar on desktop — `TabBar` handles its own responsive
+ * switch, this just positions it next to a centered, max-width content
+ * column and wraps everything in the shared React Query provider. */
+export default function AppLayout({ children }: { children: ReactNode }) {
+  return (
+    <AppQueryProvider>
+      <div className="md:flex md:min-h-screen">
+        <AppNav />
+        <main className="mx-auto w-full max-w-2xl flex-1 px-4 pb-24 pt-6 md:pb-6 md:pt-8">
+          {children}
+        </main>
+      </div>
+    </AppQueryProvider>
+  );
+}

src/app/(app)/shell.test.tsx

@@ -0,0 +1,16 @@
+import { render, screen } from "@testing-library/react";
+import { it, expect, vi } from "vitest";
+import { t } from "@/i18n/common";
+
+vi.mock("next/navigation", () => ({
+  usePathname: () => "/home",
+}));
+
+import { AppNav } from "./AppNav";
+
+it("renders all five tab labels", () => {
+  render(<AppNav />);
+  for (const label of Object.values(t.tabs)) {
+    expect(screen.getByText(label)).toBeInTheDocument();
+  }
+});

src/app/page.tsx

@@ -1,21 +1,5 @@
-import { ActionButton } from "@seed-design/react";
+import { redirect } from "next/navigation";
 
-export default function Home() {
-  return (
-    <main style={{ padding: 24 }}>
-      <h1 style={{ fontWeight: 700 }}>Mercury</h1>
-      <button
-        style={{
-          background: "var(--mercury-brand-yellow)",
-          color: "var(--mercury-on-brand)",
-          padding: "12px 20px",
-          borderRadius: 12,
-          fontWeight: 600,
-        }}
-      >
-        Холбох
-      </button>
-      <ActionButton variant="brandSolid">Seed OK</ActionButton>
-    </main>
-  );
+export default function RootPage() {
+  redirect("/home");
 }

vitest.config.ts

@@ -1,7 +1,16 @@
+import { fileURLToPath } from "node:url";
 import { defineConfig } from "vitest/config";
 import react from "@vitejs/plugin-react";
 export default defineConfig({
   plugins: [react()],
+  // Mirrors tsconfig's "@/*" -> "./src/*" path mapping (Next resolves this
+  // natively; Vite/Vitest need it spelled out) so ds/ modules that import
+  // via "@/..." (e.g. TabBar.tsx -> "@/i18n/common") resolve under Vitest too.
+  resolve: {
+    alias: {
+      "@": fileURLToPath(new URL("./src", import.meta.url)),
+    },
+  },
   test: {
     environment: "jsdom",
     setupFiles: ["./vitest.setup.ts"],