Refactor note handling to use epoch time and improve utility functions for settings management

lib/notes.dart

@@ -2,7 +2,7 @@ import 'package:intl/intl.dart';
 
 class Note {
   final String id;
-  final String date;
+  final int epochTime;
   late final String displayDate;
   String content;
   String? snippet;
@@ -11,21 +11,22 @@ class Note {
 
   Note({
     required this.id,
-    required this.date,
+    required this.epochTime,
     required this.content,
     this.snippet,
     this.isProblematic = false,
     this.problemReason = '',
   }) {
-    final dtUtc = DateFormat('yyyy-MM-dd HH:mm:ss').parse(date, true);
+    final dtUtc = DateTime.fromMillisecondsSinceEpoch(epochTime, isUtc: true);
     final dtLocal = dtUtc.toLocal();
     displayDate = DateFormat('yyyy-MM-dd HH:mm:ss').format(dtLocal);
   }
 }
 
 class Scratch {
-  final String date;
+  final int epochTime;
+  final String id;
   String content;
 
-  Scratch({required this.date, required this.content});
+  Scratch({required this.id, required this.epochTime, required this.content});
 }