feat: upgrade Angular dependencies to version 21 and implement new animation features

- Updated Angular dependencies in package.json to version 21.x.x.
- Added `provideAnimationsAsync` to app configuration for improved animation handling.
- Refactored user input component to utilize a dynamic list of vacation days with animations.
- Introduced a new `DayInput` component for managing individual vacation days.
- Enhanced styling and animations for user input and day input components.
- Updated calendar service to support new vacation day structure.
- Adjusted tests to accommodate changes in component structure and dependencies.

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

@@ -25,7 +25,61 @@
 	}
 }
 
+.listOfDays {
+	display: flex;
+	flex-direction: column;
+	gap: 0.5rem;
+}
+
+.day-input-wrapper {
+	animation: slide-fade-in 200ms ease-out;
+
+	@starting-style {
+		opacity: 0;
+		transform: translateX(-20px);
+	}
+}
+
+.day-enter {
+	animation: slide-fade-in 200ms ease-out;
+}
+
+.day-leave {
+	opacity: 0;
+	transform: translateX(20px);
+	transition:
+		opacity 200ms ease-in,
+		transform 200ms ease-in;
+}
+
+@keyframes slide-fade-in {
+	from {
+		opacity: 0;
+		transform: translateX(-20px);
+	}
+	to {
+		opacity: 1;
+		transform: translateX(0);
+	}
+}
+
 form {
 	display: flex;
 	flex-direction: column;
 }
+
+.add-day-card {
+	display: flex;
+	flex-direction: row;
+	align-items: center;
+	padding: 16px;
+	gap: 1rem;
+	margin-bottom: 1rem;
+	cursor: pointer;
+}
+
+.add-day-card h3 {
+	flex-grow: 1;
+	margin: 0;
+	font-weight: normal;
+}