Add ItemType for determining which DB methods should be called based on the screen data. Begin implementing it.

lib/models/expense.dart

@@ -1,4 +1,6 @@
 // Local
+import 'package:flutter_expense_tracker/models/item_type.dart';
+
 import '/models/tracked_item.dart';
 import '/models/frequency.dart';
 
@@ -7,6 +9,7 @@ class Expense extends TrackedItem {
 
   Expense({
     super.id,
+    super.type = ItemType.expense,
     required super.name,
     required super.amount,
     required super.frequency,

lib/models/item_type.dart

@@ -0,0 +1,22 @@
+enum ItemType {
+  expense(
+    title: "Expense",
+    plural: "Expenses",
+  ),
+  income(
+    title: "Income",
+    plural: "Incomes",
+  ),
+  asset(
+    title: "Asset",
+    plural: "Assets",
+  );
+
+  const ItemType({
+    required this.title,
+    required this.plural,
+  });
+
+  final String title;
+  final String plural;
+}

lib/models/tracked_item.dart

@@ -1,8 +1,11 @@
 // Local
+import 'package:flutter_expense_tracker/models/item_type.dart';
+
 import '/models/frequency.dart';
 
 abstract class TrackedItem {
   int? id;
+  ItemType? type;
   String name;
   double amount;
   Frequency? frequency;
@@ -10,6 +13,7 @@ abstract class TrackedItem {
 
   TrackedItem({
     this.id,
+    this.type,
     required this.name,
     required this.amount,
     this.frequency,