quite a few UX improvements

frontend/lib/modules/onbarding_agreement_card.dart

@@ -1,3 +1,4 @@
+import 'package:anyway/structs/agreement.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_markdown/flutter_markdown.dart';
 
@@ -26,7 +27,6 @@ class OnboardingAgreementCard extends StatefulWidget {
 }
 
 class _OnboardingAgreementCardState extends State<OnboardingAgreementCard> {
-  bool agreed = false;
   @override
   Widget build(BuildContext context) {
     return Padding(
@@ -39,21 +39,42 @@ class _OnboardingAgreementCardState extends State<OnboardingAgreementCard> {
           Row(
             mainAxisAlignment: MainAxisAlignment.center,
             children: [
-              Checkbox(
-                value: agreed,
-                onChanged: (value) {
-                  setState(() {
-                    agreed = value!;
-                    widget.onAgreementChanged(value);
-                  });
+              // The checkbox of the agreement
+              FutureBuilder(
+                future: getAgreement(),
+                builder: (context, snapshot) {
+                  bool agreed = false;
+                  if (snapshot.connectionState == ConnectionState.done) {
+                    if (snapshot.hasData) {
+                      Agreement agreement = snapshot.data!;
+                      agreed = agreement.agreed;
+                    } else {
+                      agreed = false;
+                    }
+                  } else {
+                    agreed = false;
+                  }
+                  return Checkbox(
+                    value: agreed,
+                    onChanged: (value) {
+                      setState(() {
+                        widget.onAgreementChanged(value!);
+                      });
+                      saveAgreement(value!);
+                    },
+                  );
                 },
               ),
+              
+              // The text of the agreement
               Text(
                 "I agree to the ",
                 style: Theme.of(context).textTheme.bodyMedium!.copyWith(
                   color: Colors.white,
                 ),
               ),
+              
+              // The clickable text of the agreement that shows the agreement text
               GestureDetector(
                 onTap: () {
                   // show a dialog with the agreement text