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

src/app/components/user-input/user-input.html

@@ -1,5 +1,5 @@
 <div class="user-input">
-	<p>Optimisez vos jours de vacances en fonction des jours fériés et des week-ends !</p>
+	<p>{{ tr().app.description }}</p>
 	<div class="listOfDays">
 		@for (day of daysOff; track day.id) {
 			<div class="day-input-wrapper" animate.enter="day-enter" animate.leave="day-leave">
@@ -11,16 +11,16 @@
 			</div>
 		}
 		<mat-card class="add-day-card mat-elevation-z2" (click)="addDay()">
-			<button matFab aria-label="Add entry">
+			<button matFab [aria-label]="tr().userInput.addVacationDay">
 				<mat-icon>add</mat-icon>
 			</button>
-			<h3>Ajouter un jour de vacances</h3>
+			<h3>{{ tr().userInput.addVacationDay }}</h3>
 		</mat-card>
 	</div>
 	<div class="action-buttons">
 		<button matFab extended (click)="triggerComputation()">
 			<mat-icon>calculate</mat-icon>
-			Calculer
+			{{ tr().userInput.calculate }}
 		</button>
 		<app-calendar-settings></app-calendar-settings>
 	</div>
@@ -31,13 +31,20 @@
 				<mat-icon color="warn">warning</mat-icon>
 				<div class="warning">
 					<span>
-						{{ remainingDays() }} jour{{ remainingDays() > 1 ? 's' : '' }} de vacances
-						non placé{{ remainingDays() > 1 ? 's' : '' }}:
+						{{
+							tr()
+								.userInput.remainingDaysWarning.replace(
+									'{count}',
+									remainingDays().toString()
+								)
+								.split('{plural}')
+								.join(remainingDays() > 1 ? 's' : '')
+						}}
 					</span>
 					@for (day of remainingDaysDetails(); track $index) {
 						<span class="remaining-day-detail">- {{ day }}</span>
 					}
-					<span> Veuillez les placer manuellement. </span>
+					<span> {{ tr().userInput.remainingDaysManualPlace }} </span>
 				</div>
 			</mat-card-content>
 		</mat-card>