- Introduced a new `i18n.js` module for handling translations and language detection, supporting both Russian and English.
- Updated various components to utilize the new translation functions, enhancing user experience by providing localized messages for errors, hints, and UI elements.
- Refactored existing code in `api.js`, `calendar.js`, `dutyList.js`, `hints.js`, and `ui.js` to replace hardcoded strings with translated messages, improving maintainability and accessibility.
- Enhanced the initialization process in `main.js` to set the document language and update UI elements based on the user's language preference.
- Updated CSS for `.day` and `.access-denied` to improve layout and visual consistency.
- Introduced a new function `dutyOverlapsLocalRange` in `dateUtils.js` to check duty overlaps within a specified date range.
- Refactored `dutyItemHtml` in `dutyList.js` to utilize `formatTimeLocal` for time formatting, enhancing readability.
- Added utility functions in `hints.js` for parsing duty marker data and building time prefixes, streamlining hint rendering logic.
- Improved the `showAccessDenied` function in `ui.js` to display detailed server messages when access is denied.
- Deleted the `app.js` file and migrated its functionality to a modular structure with multiple JavaScript files for better organization and maintainability.
- Updated `index.html` to reference the new `main.js` module, ensuring proper loading of the application.
- Introduced new utility modules for API requests, authentication, calendar handling, and DOM manipulation to enhance code clarity and separation of concerns.
- Enhanced CSS styles for improved layout and theming consistency across the application.
- Added comprehensive comments and documentation to new modules to facilitate future development and understanding.
