fix(sell): close the post-broadcast double-payment window

After broadcasting, the confirm handler fetched the order; any failure
in that fetch re-enabled Confirm with the transaction already on the
wire, so a second tap re-ran prepare, sign and broadcast and could pay
the order twice. Concurrent handlers (fee recalculation, utxo load,
order poll, price-lock refresh) also emitted pre-await snapshots that
could silently revert in-flight state.

- Latch on broadcast: payinBroadcastTxid is emitted immediately after
  the transaction is on the wire (bitcoin and liquid). A latched bloc
  never re-enters the send path, never surfaces a retryable error, and
  keeps Confirm disabled while the existing poll carries the order to
  success.
- Merge concurrent emits into live state so the latch survives fee
  recalculation, utxo loads and an order poll spanning the broadcast.
- Price-lock refresh no longer clears the in-flight flag; a failure
  after the deadline re-arms the countdown so the price refreshes.
- Show an in-flight spinner and status next to Confirm; disable
  Advanced settings during confirmation.
- Success state now carries the post-broadcast order instead of the
  stale pre-broadcast snapshot.
- Sell success screen: adds 'You sold {amount} for {fiatAmount}', gates
  the balance-credit message on balance payouts, and closes (button and
  back gesture) to wallet home like buy, on a new shared success
  scaffold widget.
- SINPE recipients: ownerName is optional, matching the server schema;
  display falls back to label, then phone or IBAN. Recipients missing
  the Ridivi-derived name are no longer dropped.

Closes #2522
Closes #2523
Closes #2529
Closes #2530

Author: FrancisPouliot

lib/core/exchange/domain/entity/order.dart

@@ -231,6 +231,21 @@ enum OrderPaymentMethod {
   final String value;
   const OrderPaymentMethod(this.value);
 
+  /// The payin/payout methods that debit or credit one of the user's in-app
+  /// fiat balances instead of an external account. Refund-to-balance methods
+  /// are deliberately excluded: they are not selectable as a payout.
+  static const balanceMethods = <OrderPaymentMethod>{
+    cadBalance,
+    eurBalance,
+    mxnBalance,
+    arsBalance,
+    copBalance,
+    crcBalance,
+    usdBalance,
+  };
+
+  bool get isBalance => balanceMethods.contains(this);
+
   static OrderPaymentMethod fromValue(String value) {
     return OrderPaymentMethod.values.firstWhere(
       (e) => e.value == value,
@@ -562,6 +577,10 @@ sealed class Order with _$Order {
   bool get isPayinCompleted => payinStatus == OrderPayinStatus.completed;
   bool get isPayoutCompleted => payoutStatus == OrderPayoutStatus.completed;
 
+  /// Whether the payout credits one of the user's in-app fiat balances rather
+  /// than an external recipient.
+  bool get isBalancePayout => payoutMethod.isBalance;
+
   bool isCompleted() => orderStatus == OrderStatus.completed;
   bool isProcessing() => orderStatus == OrderStatus.inProgress;
   bool isCancelled() => orderStatus == OrderStatus.canceled;

lib/core/widgets/success_screen_scaffold.dart

@@ -0,0 +1,112 @@
+import 'package:bb_mobile/core/themes/app_theme.dart';
+import 'package:flutter/material.dart';
+import 'package:gap/gap.dart';
+
+/// Shared layout for the exchange flows' success screens (buy, sell, pay) so
+/// they stay structurally aligned: a success icon, a headline, an optional
+/// amount line and message, and a bottom action area.
+///
+/// Back navigation is intercepted; the flow can only be left through [onClose],
+/// which is called both by the close button and by a back gesture.
+class SuccessScreenScaffold extends StatelessWidget {
+  const SuccessScreenScaffold({
+    super.key,
+    required this.title,
+    required this.headline,
+    required this.onClose,
+    this.icon,
+    this.amountLine,
+    this.message,
+    this.actions = const <Widget>[],
+  });
+
+  /// App bar title, usually the name of the flow.
+  final String title;
+
+  /// Headline under the icon, e.g. "Order completed!".
+  final String headline;
+
+  /// Leaves the flow. Called by the close button and by a back gesture.
+  final VoidCallback onClose;
+
+  /// Defaults to a large success check mark.
+  final Widget? icon;
+
+  /// Line under the headline, e.g. "You sold 100 000 sats for $50.00".
+  final String? amountLine;
+
+  /// Explanatory content under the amount line. Styled as centered body text
+  /// unless the widget overrides it, so a plain [Text] is enough.
+  final Widget? message;
+
+  /// Pinned to the bottom of the screen, typically buttons.
+  final List<Widget> actions;
+
+  @override
+  Widget build(BuildContext context) {
+    return PopScope(
+      canPop: false,
+      onPopInvokedWithResult: (didPop, _) {
+        if (didPop) return;
+        onClose();
+      },
+      child: Scaffold(
+        appBar: AppBar(
+          title: Text(title),
+          automaticallyImplyLeading: false,
+          actions: [
+            IconButton(icon: const Icon(Icons.close), onPressed: onClose),
+          ],
+        ),
+        body: SafeArea(
+          child: Center(
+            child: Padding(
+              padding: const EdgeInsets.symmetric(horizontal: 24.0),
+              child: Column(
+                mainAxisAlignment: .center,
+                children: [
+                  icon ??
+                      Icon(
+                        Icons.check_circle,
+                        size: 100,
+                        color: context.appColors.success,
+                      ),
+                  const Gap(20),
+                  Text(
+                    headline,
+                    style: context.font.titleLarge,
+                    textAlign: .center,
+                  ),
+                  if (amountLine != null) ...[
+                    const Gap(8),
+                    Text(
+                      amountLine!,
+                      style: context.font.bodyLarge,
+                      textAlign: .center,
+                    ),
+                  ],
+                  if (message != null) ...[
+                    const Gap(10),
+                    DefaultTextStyle.merge(
+                      style: context.font.bodyMedium,
+                      textAlign: .center,
+                      child: message!,
+                    ),
+                  ],
+                ],
+              ),
+            ),
+          ),
+        ),
+        bottomNavigationBar: actions.isEmpty
+            ? null
+            : SafeArea(
+                child: Padding(
+                  padding: const EdgeInsets.all(16.0),
+                  child: Column(mainAxisSize: .min, children: actions),
+                ),
+              ),
+      ),
+    );
+  }
+}

lib/features/recipients/application/dtos/recipient_details_dto.dart

@@ -397,49 +397,43 @@ class RecipientDetailsDto {
         );
 
       // COSTA RICA
+      // ownerName is nullable by design for the SINPE types: the server fills it
+      // from a Ridivi lookup that can fail or be empty on older records.
+      // Requiring it here silently dropped those recipients (#2529).
       case RecipientType.sinpeIbanUsd:
         if (iban == null) {
           throw StateError('iban is required for SINPE_IBAN_USD.');
         }
-        if (ownerName == null) {
-          throw StateError('ownerName is required for SINPE_IBAN_USD.');
-        }
         return SinpeIbanUsdDetails.create(
           label: label,
           isDefault: def,
           isOwner: isOwner,
           iban: iban!,
-          ownerName: ownerName!,
+          ownerName: ownerName,
         );
 
       case RecipientType.sinpeIbanCrc:
         if (iban == null) {
           throw StateError('iban is required for SINPE_IBAN_CRC.');
         }
-        if (ownerName == null) {
-          throw StateError('ownerName is required for SINPE_IBAN_CRC.');
-        }
         return SinpeIbanCrcDetails.create(
           label: label,
           isDefault: def,
           isOwner: isOwner,
           iban: iban!,
-          ownerName: ownerName!,
+          ownerName: ownerName,
         );
 
       case RecipientType.sinpeMovilCrc:
         if (phoneNumber == null) {
           throw StateError('phoneNumber is required for SINPE_MOVIL_CRC.');
         }
-        if (ownerName == null) {
-          throw StateError('ownerName is required for SINPE_MOVIL_CRC.');
-        }
         return SinpeMovilCrcDetails.create(
           label: label,
           isDefault: def,
           isOwner: isOwner,
           phoneNumber: phoneNumber!,
-          ownerName: ownerName!,
+          ownerName: ownerName,
         );
 
       // ARGENTINA

lib/features/recipients/domain/value_objects/recipient_details.dart

@@ -378,39 +378,45 @@ class SpeiCardMxnDetails extends RecipientDetails {
 }
 
 // ── SINPE (CRC/USD)
+//
+// The owner name comes from a Ridivi lookup on the server, which can fail or be
+// empty on older records, so it is nullable by design (#2529). Display sites
+// fall back to the label and then to the account identifier.
+String? _nullIfBlank(String? value) {
+  final trimmed = value?.trim();
+  return trimmed == null || trimmed.isEmpty ? null : trimmed;
+}
+
 @immutable
 class SinpeIbanUsdDetails extends RecipientDetails {
   final String iban;
-  final String ownerName;
+  final String? ownerName;
 
   const SinpeIbanUsdDetails._({
     super.label,
     super.isDefault = false,
     super.isOwner,
     required this.iban,
-    required this.ownerName,
+    this.ownerName,
   });
 
   factory SinpeIbanUsdDetails.create({
     String? label,
     bool isDefault = false,
     bool? isOwner,
     required String iban,
-    required String ownerName,
+    String? ownerName,
   }) {
     if (iban.trim().isEmpty) {
       throw ArgumentError('IBAN cannot be empty');
     }
-    if (ownerName.trim().isEmpty) {
-      throw ArgumentError('Owner name cannot be empty');
-    }
 
     return SinpeIbanUsdDetails._(
       label: label,
       isDefault: isDefault,
       isOwner: isOwner,
       iban: iban.trim(),
-      ownerName: ownerName.trim(),
+      ownerName: _nullIfBlank(ownerName),
     );
   }
 
@@ -421,36 +427,33 @@ class SinpeIbanUsdDetails extends RecipientDetails {
 @immutable
 class SinpeIbanCrcDetails extends RecipientDetails {
   final String iban;
-  final String ownerName;
+  final String? ownerName;
 
   const SinpeIbanCrcDetails._({
     super.label,
     super.isDefault = false,
     super.isOwner,
     required this.iban,
-    required this.ownerName,
+    this.ownerName,
   });
 
   factory SinpeIbanCrcDetails.create({
     String? label,
     bool isDefault = false,
     bool? isOwner,
     required String iban,
-    required String ownerName,
+    String? ownerName,
   }) {
     if (iban.trim().isEmpty) {
       throw ArgumentError('IBAN cannot be empty');
     }
-    if (ownerName.trim().isEmpty) {
-      throw ArgumentError('Owner name cannot be empty');
-    }
 
     return SinpeIbanCrcDetails._(
       label: label,
       isDefault: isDefault,
       isOwner: isOwner,
       iban: iban.trim(),
-      ownerName: ownerName.trim(),
+      ownerName: _nullIfBlank(ownerName),
     );
   }
 
@@ -461,36 +464,33 @@ class SinpeIbanCrcDetails extends RecipientDetails {
 @immutable
 class SinpeMovilCrcDetails extends RecipientDetails {
   final String phoneNumber;
-  final String ownerName;
+  final String? ownerName;
 
   const SinpeMovilCrcDetails._({
     super.label,
     super.isDefault = false,
     super.isOwner,
     required this.phoneNumber,
-    required this.ownerName,
+    this.ownerName,
   });
 
   factory SinpeMovilCrcDetails.create({
     String? label,
     bool isDefault = false,
     bool? isOwner,
     required String phoneNumber,
-    required String ownerName,
+    String? ownerName,
   }) {
     if (phoneNumber.trim().isEmpty) {
       throw ArgumentError('Phone number cannot be empty');
     }
-    if (ownerName.trim().isEmpty) {
-      throw ArgumentError('Owner name cannot be empty');
-    }
 
     return SinpeMovilCrcDetails._(
       label: label,
       isDefault: isDefault,
       isOwner: isOwner,
       phoneNumber: phoneNumber.trim(),
-      ownerName: ownerName.trim(),
+      ownerName: _nullIfBlank(ownerName),
     );
   }
 

lib/features/recipients/interface_adapters/presenters/models/recipient_view_model.dart

@@ -138,19 +138,21 @@ sealed class RecipientViewModel with _$RecipientViewModel {
         if (label != null && label!.isNotEmpty) return label!;
         return null;
 
+      // ownerName is often absent for the SINPE types (#2529), so fall all the
+      // way back to the account identifier rather than showing nothing.
       case RecipientType.sinpeIbanUsd:
-        if (ownerName != null && ownerName!.isNotEmpty) return ownerName!;
-        if (label != null && label!.isNotEmpty) return label!;
-        return null;
-
       case RecipientType.sinpeIbanCrc:
         if (ownerName != null && ownerName!.isNotEmpty) return ownerName!;
         if (label != null && label!.isNotEmpty) return label!;
+        if (iban != null && iban!.isNotEmpty) return iban!;
         return null;
 
       case RecipientType.sinpeMovilCrc:
         if (ownerName != null && ownerName!.isNotEmpty) return ownerName!;
         if (label != null && label!.isNotEmpty) return label!;
+        if (phoneNumber != null && phoneNumber!.isNotEmpty) {
+          return phoneNumber!;
+        }
         return null;
       case RecipientType.bankAccountArgentina:
         if (name != null && name!.isNotEmpty) return name!;