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>

---------

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

---------

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.scss

@@ -51,25 +51,32 @@
 	}
 }
 
+.spinner-container {
+	position: relative;
+	display: inline-block;
+
+	::ng-deep .mat-mdc-progress-spinner {
+		// Override Material spinner size
+		width: 100px;
+		height: 100px;
+	}
+
+	.spinner-text {
+		position: absolute;
+		top: 50%;
+		left: 50%;
+		transform: translate(-50%, -50%);
+		font-size: 20px;
+		font-weight: bold;
+		color: #333;
+		pointer-events: none;
+
+		@media (prefers-color-scheme: dark) {
+			color: #ddd;
+		}
+	}
+}
+
 .card {
 	margin: 16px;
 }
-
-@keyframes spin {
-	0% {
-		transform: rotate(0deg);
-	}
-
-	100% {
-		transform: rotate(360deg);
-	}
-}
-
-:root {
-	@include mat.progress-spinner-overrides(
-		(
-			size: 0.5rem,
-			active-indicator-width: 0.25rem,
-		)
-	);
-}