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/Parsers/EventOccurrenceGrammar.cs

@@ -14,11 +14,11 @@ public static class EventOccurrenceGrammar
     /// Array of all month names in order (January through December).
     /// This is the single source of truth for month names used throughout the parser.
     /// </summary>
-    public static readonly string[] MonthNames = new[]
-    {
+    public static readonly string[] MonthNames =
+    [
         "January", "February", "March", "April", "May", "June",
         "July", "August", "September", "October", "November", "December"
-    };
+    ];
 
     // Build month parsers dynamically from MonthNames array
     private static readonly Parser<string>[] MonthParsers = MonthNames

Core/Parsers/StudentEventRankingParser.cs

@@ -27,7 +27,7 @@ public class StudentEventRankingParser : CsvParserBase
                 continue;
             
 
-            var competitiveEvents = new List<EventDefinition>(6);
+            var competitiveEvents = new List<EventDefinition>();
 
             for (var i = 1; i <= 6; i++)
             {

Core/Parsers/StudentParser.cs

@@ -13,7 +13,7 @@ public class StudentParser : CsvParserBase
 
     public Student[] Parse()
     {
-        var s = new List<Student>();
+        var students = new List<Student>();
 
         CsvReader.Read();
         CsvReader.ReadHeader();
@@ -44,9 +44,9 @@ public class StudentParser : CsvParserBase
                 RegionalId = regionalId,
                 NationalId = nationalId
             };
-            s.Add(student);
+            students.Add(student);
 		}
 
-        return s.ToArray();
+        return students.ToArray();
     }
 }