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

lib/pages/home.dart

@@ -1,14 +1,14 @@
 // Flutter
 import 'package:flutter/material.dart';
+import 'package:flutter_expense_tracker/models/item_type.dart';
 import 'dart:io';
 
 // Local
-import '/pages/expense.dart';
-import '/pages/income.dart';
-import '/pages/asset.dart';
+import '/pages/tracked_item.dart';
 import '/pages/report.dart';
 import '/pages/settings.dart';
 import '/pages/help.dart';
+import '/db.dart';
 
 class HomePage extends StatefulWidget {
   const HomePage({
@@ -32,14 +32,15 @@ class _HomePageState extends State<HomePage> {
     Widget? dialog;
     switch (pageSelected) {
       case 0:
-        page = ExpensePage();
+        page = TrackedItemPage(assetsToLoad: DatabaseHelper.instance.getExpenses());
         dialog = TrackedItemInputDialog(
           notifyParent: refresh,
+          type: ItemType.expense,
         );
       case 1:
-        page = IncomePage();
+        page = Placeholder();
       case 2:
-        page = AssetPage();
+        page = Placeholder();
       case 3:
         page = ProjectionPage();
       case 4: