feat: implement internationalization with multi-language support and runtime language selection

src/app/components/calendar-month/calendar-month.html

@@ -5,13 +5,9 @@
 			@if (calendarSettingsService.get('showWeekNumbers')()) {
 				<p class="day empty week-number"></p>
 			}
-			<p class="day">L</p>
-			<p class="day">M</p>
-			<p class="day">M</p>
-			<p class="day">J</p>
-			<p class="day">V</p>
-			<p class="day">S</p>
-			<p class="day">D</p>
+			@for (letter of getWeekdayLetters(); track $index) {
+				<p class="day">{{ letter }}</p>
+			}
 		</div>
 		<div class="cols">
 			@for (week of weeksInAMonth; track $index) {
@@ -36,7 +32,7 @@
 								[class.selected]="selectedDates.isSelected(day)"
 								[class]="selectedDates.getClasses(day)"
 								class="day number"
-								[matTooltip]="selectedDates.getTooltip(day)"
+								[matTooltip]="getDayTooltip(day)"
 								[matTooltipShowDelay]="500"
 							>
 								{{ day.getDate() }}