feat: enhance loading spinner with progress indication and add warnin… (#49)

* feat: enhance loading spinner with progress indication and add warning for unplaced vacation days

* Update src/app/services/calendar-service.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/app/components/calendar-year/calendar-year.scss

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Fix setTimeout async anti-pattern in calendar-year component (#50)

* Initial plan

* fix: replace setTimeout async anti-pattern with queueMicrotask and void

Co-authored-by: THoguet <61246905+THoguet@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: THoguet <61246905+THoguet@users.noreply.github.com>

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>

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

@@ -2,7 +2,10 @@
 	@if (isLoading()) {
 		<div class="loading-overlay">
 			<div class="loading-spinner">
-				<mat-spinner></mat-spinner>
+				<div class="spinner-container">
+					<mat-spinner [mode]="'determinate'" [value]="loadingProgress()"></mat-spinner>
+					<div class="spinner-text">{{ loadingProgress() }}%</div>
+				</div>
 				<p>Calcul en cours...</p>
 			</div>
 		</div>