refactor: Move constructor to the top of the Benefit class for improved readability

apps/mobile/packages/domain/lib/src/entities/benefits/benefit.dart

@@ -2,6 +2,13 @@ import 'package:equatable/equatable.dart';
 
 /// Represents a staff member's benefit balance.
 class Benefit extends Equatable {
+  /// Creates a [Benefit].
+  const Benefit({
+    required this.title,
+    required this.entitlementHours,
+    required this.usedHours,
+  });
+
   /// The title of the benefit (e.g., Sick Leave, Holiday, Vacation).
   final String title;
 
@@ -14,13 +21,6 @@ class Benefit extends Equatable {
   /// The hours remaining.
   double get remainingHours => entitlementHours - usedHours;
 
-  /// Creates a [Benefit].
-  const Benefit({
-    required this.title,
-    required this.entitlementHours,
-    required this.usedHours,
-  });
-
   @override
   List<Object?> get props => [title, entitlementHours, usedHours];
 }