feat(renderer): add next-themes provider + theme toggle (sun/moon)

tests/component/theme-toggle.test.tsx

@@ -0,0 +1,40 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { ThemeProvider } from '@/components/theme-provider';
+import { ThemeToggle } from '@/components/theme-toggle';
+
+Object.defineProperty(window, 'matchMedia', {
+  writable: true,
+  value: vi.fn().mockImplementation((query) => ({
+    matches: false,
+    media: query,
+    onchange: null,
+    addListener: vi.fn(),
+    removeListener: vi.fn(),
+    addEventListener: vi.fn(),
+    removeEventListener: vi.fn(),
+    dispatchEvent: vi.fn(),
+  })),
+});
+
+describe('ThemeToggle', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    document.documentElement.classList.remove('dark', 'light');
+  });
+
+  it('toggles between light and dark when clicked', async () => {
+    render(
+      <ThemeProvider defaultTheme="light" attribute="class">
+        <ThemeToggle />
+      </ThemeProvider>
+    );
+    const btn = screen.getByRole('button');
+    expect(btn).toHaveAccessibleName(/toggle theme/i);
+    await userEvent.click(btn);
+    expect(document.documentElement.classList.contains('dark')).toBe(true);
+    await userEvent.click(btn);
+    expect(document.documentElement.classList.contains('light')).toBe(true);
+  });
+});