feat: enhance current duty display with remaining time and improved contact links

- Added a new message key for displaying remaining time until the end of the shift in both English and Russian.
- Updated the current duty card to show remaining time with a formatted string.
- Enhanced the contact links to support block layout with icons for phone and Telegram, improving visual presentation.
- Implemented a new utility function to calculate remaining time until the end of the shift.
- Added unit tests for the new functionality, ensuring accurate time calculations and proper rendering of contact links.

duty_teller/i18n/messages.py

@@ -93,6 +93,7 @@ MESSAGES: dict[str, dict[str, str]] = {
         "current_duty.title": "Current Duty",
         "current_duty.no_duty": "No one is on duty right now",
         "current_duty.shift": "Shift",
+        "current_duty.remaining": "Remaining: {hours}h {minutes}min",
         "current_duty.back": "Back to calendar",
     },
     "ru": {
@@ -175,6 +176,7 @@ MESSAGES: dict[str, dict[str, str]] = {
         "current_duty.title": "Текущее дежурство",
         "current_duty.no_duty": "Сейчас никто не дежурит",
         "current_duty.shift": "Смена",
+        "current_duty.remaining": "Осталось: {hours}ч {minutes}мин",
         "current_duty.back": "Назад к календарю",
     },
 }