feat(website): add next-intl i18n and dark mode support

website/src/components/__tests__/theme-toggle.test.tsx

@@ -0,0 +1,50 @@
+// @vitest-environment jsdom
+import { render, screen, fireEvent } from "@testing-library/react";
+import { ThemeToggle } from "../theme-toggle";
+import { describe, it, expect, vi } from "vitest";
+import * as nextThemes from "next-themes";
+
+// Mock next-themes
+vi.mock("next-themes", async () => {
+  const actual = await vi.importActual("next-themes");
+  return {
+    ...actual,
+    useTheme: vi.fn(),
+  };
+});
+
+describe("ThemeToggle", () => {
+  it("calls setTheme to dark when current theme is light", () => {
+    // given
+    const setThemeMock = vi.fn();
+    (nextThemes.useTheme as unknown as ReturnType<typeof vi.fn>).mockReturnValue({
+      theme: "light",
+      setTheme: setThemeMock,
+    });
+
+    // when
+    render(<ThemeToggle />);
+    const button = screen.getByRole("button", { name: /toggle theme/i });
+    fireEvent.click(button);
+
+    // then
+    expect(setThemeMock).toHaveBeenCalledWith("dark");
+  });
+
+  it("calls setTheme to light when current theme is dark", () => {
+    // given
+    const setThemeMock = vi.fn();
+    (nextThemes.useTheme as unknown as ReturnType<typeof vi.fn>).mockReturnValue({
+      theme: "dark",
+      setTheme: setThemeMock,
+    });
+
+    // when
+    render(<ThemeToggle />);
+    const button = screen.getByRole("button", { name: /toggle theme/i });
+    fireEvent.click(button);
+
+    // then
+    expect(setThemeMock).toHaveBeenCalledWith("light");
+  });
+});