better errorhandling, slimmed down optimizer

frontend/lib/pages/profile.dart

@@ -1,3 +1,4 @@
+import 'package:anyway/constants.dart';
 import 'package:anyway/structs/preferences.dart';
 import 'package:flutter/material.dart';
 
@@ -24,6 +25,32 @@ class _ProfilePageState extends State<ProfilePage> {
             onChanged: (bool? newValue) {
               setState(() {
                 debugMode = newValue!;
+                showDialog(
+                  context: context,
+                  builder: (BuildContext context) {
+                    return AlertDialog(
+                      title: Text('Debug mode - custom API'),
+                      content: TextField(
+                        decoration: InputDecoration(
+                          hintText: 'http://localhost:8000'
+                        ),
+                      onChanged: (value) {
+                        setState(() {
+                          API_URL_BASE = value;
+                        });
+                      },
+                    ),
+                    actions: [
+                      TextButton(
+                        child: Text('OK'),
+                        onPressed: () {
+                          Navigator.of(context).pop();
+                        },
+                      ),
+                    ],
+                    );
+                  }
+                );
               });
             }
           )