Initialize project with basic structure, including Docker configuration, backend and frontend setup, environment configuration, and essential files for development.

frontend/src/i18n.test.tsx

@@ -0,0 +1,27 @@
+import { cleanup, fireEvent, render, screen, waitFor } from '@testing-library/react'
+import { afterEach, describe, expect, it } from 'vitest'
+import { LanguageProvider, LanguageSelector } from './i18n'
+
+afterEach(() => {
+  cleanup()
+  localStorage.clear()
+})
+
+describe('runtime language selection', () => {
+  it('switches UI text to Russian and persists the choice', async () => {
+    localStorage.setItem('mixmaker-language', 'en')
+    render(<LanguageProvider><LanguageSelector /><p>Your events</p></LanguageProvider>)
+    fireEvent.change(screen.getByRole('combobox'), { target: { value: 'ru' } })
+    await waitFor(() => expect(screen.getByText('Ваши события')).toBeInTheDocument())
+    expect(localStorage.getItem('mixmaker-language')).toBe('ru')
+    expect(document.documentElement.lang).toBe('ru')
+  })
+
+  it('restores English after switching back', async () => {
+    localStorage.setItem('mixmaker-language', 'ru')
+    render(<LanguageProvider><LanguageSelector /><p>Your events</p></LanguageProvider>)
+    await waitFor(() => expect(screen.getByText('Ваши события')).toBeInTheDocument())
+    fireEvent.change(screen.getByRole('combobox'), { target: { value: 'en' } })
+    await waitFor(() => expect(screen.getByText('Your events')).toBeInTheDocument())
+  })
+})