update values logic

frontend/lib/pages/add.dart

@@ -2,7 +2,8 @@ import 'package:flutter/material.dart';
 import 'package:frontend/provider/quote_provider.dart';
 import 'package:frontend/model/quote.dart';
 
-import 'package:frontend/strings.dart';
+import 'package:frontend/values/strings.dart';
+import 'package:frontend/values/constants.dart';
 
 class AddPage extends StatelessWidget {
   const AddPage({super.key});
@@ -13,9 +14,9 @@ class AddPage extends StatelessWidget {
     final authorController = TextEditingController(text: '');
     final provider = QuoteProvider();
     return Card(
-      margin: const EdgeInsets.all(16),
+      margin: const EdgeInsets.all(Constants.edgeInset),
       child: Padding(
-        padding: const EdgeInsets.all(16),
+        padding: const EdgeInsets.all(Constants.edgeInset),
         child: Column(
           mainAxisSize: MainAxisSize.min,
           crossAxisAlignment: CrossAxisAlignment.start,

frontend/lib/values/constants.dart

@@ -0,0 +1,3 @@
+class Constants {
+  static const double edgeInset = 16;
+}