feat: Add color and icon properties to categories, enhance category management in UI

lib/models/category.dart

@@ -8,6 +8,8 @@ class Category {
     this.isDeleted = false,
     required this.updatedAt,
     this.isDirty = true,
+    this.colorValue,
+    this.iconCodePoint,
   }) : id = id ?? Uuid().v4();
 
   final String id;
@@ -16,6 +18,8 @@ class Category {
   final bool isDeleted;
   final DateTime updatedAt;
   final bool isDirty;
+  final int? colorValue;
+  final int? iconCodePoint;
 
   Category copyWith({
     String? id,
@@ -24,6 +28,8 @@ class Category {
     bool? isDeleted,
     DateTime? updatedAt,
     bool? isDirty,
+    int? colorValue,
+    int? iconCodePoint,
   }) {
     return Category(
       id: id ?? this.id,
@@ -32,6 +38,8 @@ class Category {
       isDeleted: isDeleted ?? this.isDeleted,
       updatedAt: updatedAt ?? this.updatedAt,
       isDirty: isDirty ?? this.isDirty,
+      colorValue: colorValue ?? this.colorValue,
+      iconCodePoint: iconCodePoint ?? this.iconCodePoint,
     );
   }