Fix quiz page scroll anchor

Adjusted QuizPage to prevent body-level scrolling and ensure quiz content scrolls within its own area under sticky header. Added targeted overflow/viewport handling, moved quiz content to a scrollable container, and applied guards to avoid unintended page scroll on small screens.

X-Lovable-Edit-ID: edt-dbe6286c-b3af-48f7-94d6-a111f68484b6
Co-authored-by: ildu00 <163680508+ildu00@users.noreply.github.com>

Обновил README.md документацию

Подробно описал возможности проекта, темы, технологии, источник данных, запуск локально и структуру проекта на русском языке.

X-Lovable-Edit-ID: edt-e4c2c544-26c0-4e5a-8ff8-74273ca378ec
Co-authored-by: ildu00 <163680508+ildu00@users.noreply.github.com>