Add optional KYC flow and service-backed account limits

frontend/app/lib/kyc/form.dart

@@ -0,0 +1,87 @@
+import 'package:flutter/material.dart';
+
+import 'package:sxchnge_kyc/sxchnge_kyc.dart';
+
+import 'photo.dart';
+
+import '../generated/i18n/app_localizations.dart';
+
+class IdentityForm extends StatelessWidget {
+  const IdentityForm({super.key, required this.provider});
+  final IdentityProvider provider;
+  @override
+  Widget build(BuildContext context) {
+    final p = provider;
+    final l = AppLocalizations.of(context)!;
+    final titles = [l.kycPassport, l.kycSelfie, l.kycReview];
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: [
+        Semantics(
+          header: true,
+          liveRegion: true,
+          child: Text(
+            '${p.step + 1} / 3 · ${titles[p.step]}',
+            style: Theme.of(context).textTheme.headlineSmall,
+          ),
+        ),
+        const SizedBox(height: 16),
+        LinearProgressIndicator(
+          value: (p.step + 1) / 3,
+          semanticsLabel: titles[p.step],
+        ),
+        const SizedBox(height: 16),
+        if (p.step < 2)
+          PhotoPanel(
+            kind: p.step == 0 ? PhotoKind.passport : PhotoKind.selfie,
+            photo: p.step == 0 ? p.passport : p.selfie,
+            onPick: p.busy
+                ? null
+                : () => p.pick(
+                    p.step == 0 ? PhotoKind.passport : PhotoKind.selfie,
+                  ),
+            onRemove: p.busy
+                ? null
+                : () => p.remove(
+                    p.step == 0 ? PhotoKind.passport : PhotoKind.selfie,
+                  ),
+          ),
+        if (p.step == 2) ...[
+          Text(l.kycReviewHelp),
+          const SizedBox(height: 16),
+          PhotoPanel(kind: PhotoKind.passport, photo: p.passport, review: true),
+          PhotoPanel(kind: PhotoKind.selfie, photo: p.selfie, review: true),
+          CheckboxListTile(
+            contentPadding: EdgeInsets.zero,
+            controlAffinity: ListTileControlAffinity.leading,
+            value: p.confirmed,
+            onChanged: p.busy ? null : (v) => p.confirm(v ?? false),
+            title: Text(l.kycConfirm),
+          ),
+        ],
+        const SizedBox(height: 16),
+        if (p.step < 2) ...[
+          if ((p.step == 0 ? p.passport : p.selfie) == null)
+            Padding(
+              padding: const EdgeInsets.only(bottom: 12),
+              child: Text(l.kycChooseFirst),
+            ),
+          FilledButton(
+            key: const ValueKey('kyc-next'),
+            onPressed: p.busy || (p.step == 0 ? p.passport : p.selfie) == null
+                ? null
+                : p.next,
+            child: Text(l.kycNext),
+          ),
+        ] else
+          FilledButton(
+            key: const ValueKey('kyc-submit'),
+            onPressed: p.canSubmit ? p.submit : null,
+            child: Text(p.isDemo ? l.kycSubmitDemo : l.kycSubmit),
+          ),
+        if (p.step > 0)
+          TextButton(onPressed: p.busy ? null : p.back, child: Text(l.kycBack)),
+      ],
+    );
+  }
+}