Add reusable two-factor verification for login and money operations (#32)

frontend/app/lib/security/settings.dart

@@ -0,0 +1,98 @@
+import 'package:flutter/material.dart';
+
+import 'package:provider/provider.dart';
+
+import 'package:sxchnge_analytics/sxchnge_analytics.dart';
+
+import 'package:sxchnge_auth/sxchnge_auth.dart';
+
+import 'challenge.dart';
+
+import '../generated/i18n/app_localizations.dart';
+
+class SecuritySettings extends StatefulWidget {
+  const SecuritySettings({super.key});
+  @override
+  State<SecuritySettings> createState() => _SecuritySettingsState();
+}
+
+class _SecuritySettingsState extends State<SecuritySettings> {
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (mounted) context.read<SecurityProvider>().refresh();
+    });
+  }
+
+  Future<void> _change(SecurityProvider p, bool enabled) async {
+    final challenge = await p.prepare(enabled);
+    if (!mounted || challenge == null) return;
+    final grant = await verifyFactor(
+      context,
+      challenge: challenge,
+      service: p.service,
+      recorder: p.recorder,
+      journey: JourneyKind.security,
+    );
+    if (mounted && grant != null) await p.apply(enabled, grant);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final p = context.watch<SecurityProvider>();
+    final l = AppLocalizations.of(context)!;
+    final t = Theme.of(context);
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(24),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            Text(l.factorSettings, style: t.textTheme.titleLarge),
+            const SizedBox(height: 12),
+            Text(l.factorSettingsHelp),
+            const SizedBox(height: 16),
+            if (p.busy) const LinearProgressIndicator(),
+            if (p.data != null) ...[
+              Semantics(
+                liveRegion: true,
+                child: Text(
+                  p.data!.enabled ? l.factorOn : l.factorOff,
+                  key: const ValueKey('two-factor-status'),
+                  style: t.textTheme.titleMedium,
+                ),
+              ),
+              const SizedBox(height: 8),
+              Text(
+                p.data!.method == FactorMethod.email
+                    ? l.factorEmailMethod
+                    : l.factorAppMethod,
+              ),
+              const SizedBox(height: 16),
+              FilledButton.tonal(
+                key: const ValueKey('two-factor-setting'),
+                onPressed: p.busy ? null : () => _change(p, !p.data!.enabled),
+                child: Text(p.data!.enabled ? l.factorDisable : l.factorEnable),
+              ),
+            ],
+            if (p.error != null) ...[
+              const SizedBox(height: 12),
+              Semantics(
+                liveRegion: true,
+                child: Text(
+                  factorErrorText(l, p.error!),
+                  style: TextStyle(color: t.colorScheme.error),
+                ),
+              ),
+              TextButton(
+                onPressed: p.busy ? null : p.refresh,
+                child: Text(l.wRefresh),
+              ),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}