Refactor collection initializers to use C# 12 collection expressions

This commit updates various files across the Core and WebApp projects to replace traditional collection initializers with C# 12 collection expressions. Changes include modifications to EventAssignment.cs, TeamScheduler_DecisionTree.cs, CareerField.cs, EventDefinition.cs, and several components in the WebApp. These updates enhance code readability and maintainability by adhering to modern C# syntax standards.

Core/Calculation/EventAssignment.cs

@@ -254,7 +254,7 @@ namespace Core.Calculation
         private void AddStudentConstraint(CpModel model, BoolVar[,] x,
             Func<EventDefinition, bool> eventFilter, Action<CpModel, List<ILiteral>> constraintAction)
         {
-            var buffer = new List<ILiteral>();
+            List<ILiteral> buffer = [];
             foreach (var s in _allStudents)
             {
                 buffer.Clear();
@@ -273,7 +273,7 @@ namespace Core.Calculation
         /// </summary>
         private void IndividualEventsMustBeRanked(CpModel model, BoolVar[,] x)
         {
-            var prohibitVar = new List<IntVar>(1);
+            List<IntVar> prohibitVar = [];
 
             foreach (var s in _allStudents)
             {
@@ -328,7 +328,7 @@ namespace Core.Calculation
         /// </summary>
         private void LimitStudentAssignment(CpModel model, BoolVar[,] x)
         {
-            var studentCapacity = new List<IntVar>();
+            List<IntVar> studentCapacity = [];
 
             foreach (var s in _allStudents)
             {
@@ -418,7 +418,7 @@ namespace Core.Calculation
         /// </summary>
         private void AddEventConstraint(CpModel model, BoolVar[,] x, int eventIndex, int lb, int ub)
         {
-            var eventCapacity = new List<IntVar>();
+            List<IntVar> eventCapacity = [];
             foreach (var s in _allStudents)
             {
                 eventCapacity.Add(x[eventIndex, s]);
@@ -455,7 +455,7 @@ namespace Core.Calculation
                 model.AddAssumption(x[e, s]);
             }
 
-            var prohibitVar = new List<IntVar>(1);
+            List<IntVar> prohibitVar = [];
             foreach (var excludedAssignment in _assignmentRequirements.Where(a => a.Requirement == Requirement.Exclude))
             {
                 var e = _events.IndexOf(excludedAssignment.EventDefinition);