Begin working on the database.

lib/pages/expense.dart

@@ -1,5 +1,7 @@
+// Flutter
 import 'package:flutter/material.dart';
 
+// Local
 import '/models/expense.dart';
 import '/models/frequency.dart';
 
@@ -61,6 +63,7 @@ class _ExpenseInputDialogState extends State<ExpenseInputDialog> {
 
   @override
   Widget build(BuildContext context) {
+    // TODO: Do this as a values.map().
     List<DropdownMenuItem> freqValues = [];
     for (var freq in Frequency.values) {
       freqValues.add(DropdownMenuItem(value: freq, child: Text(freq.title)));