fix(shopinbit): migrate car research flow to API v1.0.6

diff --git a/lib/pages/shopinbit/shopinbit_car_fee_view.dart b/lib/pages/shopinbit/shopinbit_car_fee_view.dart
index 60ea3f4..c297be0 100644
--- a/lib/pages/shopinbit/shopinbit_car_fee_view.dart
+++ b/lib/pages/shopinbit/shopinbit_car_fee_view.dart
@@ -315,9 +315,8 @@ class _ShopInBitCarFeeViewState extends ConsumerState<ShopInBitCarFeeView> {
   }
 
   Future<void> _loadFee(CarResearchInvoice invoice) async {
-    // Keep status call for visibility into any future API changes surfacing
-    // a fee field. Today the endpoint returns only {status, additional}, so
-    // we source the displayed amount from the BIP21 payment URIs instead.
+    // Still hit status for logging; it has no fee field, so the amount comes
+    // from the BIP21 payment URIs.
     try {
       final resp = await ref
           .read(pShopinBitService)
diff --git a/lib/pages/shopinbit/shopinbit_car_research_payment_view.dart b/lib/pages/shopinbit/shopinbit_car_research_payment_view.dart
index d8f78bd..08c81eb 100644
--- a/lib/pages/shopinbit/shopinbit_car_research_payment_view.dart
+++ b/lib/pages/shopinbit/shopinbit_car_research_payment_view.dart
@@ -50,10 +50,15 @@ class _ShopInBitCarResearchPaymentViewState
   static const Duration _kMaxPollInterval = Duration(seconds: 120);
   Duration _pollInterval = _kBasePollInterval;
 
-  Map<String, dynamic>? _status;
+  CarResearchInvoiceStatus? _status;
   _PaymentFlowState _flowState = _PaymentFlowState.idle;
   String _statusString = "ready_to_pay";
   String? _additional;
+  bool _finalized = false;
+  // From the finalized status: the real ticket is the customer chat, the
+  // receipt is just the paid-fee receipt.
+  int? _realTicketId;
+  int? _receiptTicketId;
   List<String> _methods = [];
   List<String> _addresses = [];
   int _selectedMethod = 0;
@@ -61,7 +66,9 @@ class _ShopInBitCarResearchPaymentViewState
   String get _currentAddress =>
       _selectedMethod < _addresses.length ? _addresses[_selectedMethod] : "";
 
-  bool get _isTerminal => carResearchIsFinalized(_statusString, _additional);
+  // Trust the `finalized` flag; fall back to the status/additional heuristic.
+  bool get _isTerminal =>
+      _finalized || carResearchIsFinalized(_statusString, _additional);
 
   bool get _payNowEnabled =>
       !_isTerminal && _flowState == _PaymentFlowState.idle;
@@ -145,10 +152,9 @@ class _ShopInBitCarResearchPaymentViewState
   }
 
   String get _displayedFee {
-    // API status endpoint does not expose a fee field (confirmed: returns
-    // only {status, additional}). Parse the amount from the BIP21 payment
-    // URI for the currently-selected method, fall back to the 223.00 EUR
-    // business-rule value if no parse succeeds.
+    // The status endpoint has no fee field, so parse the amount from the
+    // selected method's BIP21 URI, falling back to the 223.00 EUR business
+    // rule.
     final links = widget.invoice.paymentLinks;
     if (_selectedMethod < _methods.length) {
       final methodKey = _methods[_selectedMethod];
@@ -339,8 +345,13 @@ class _ShopInBitCarResearchPaymentViewState
       );
       setState(() {
         _status = resp.value!;
-        _statusString = _status!["status"]?.toString() ?? _statusString;
-        _additional = _status!["additional"]?.toString();
+        _statusString = _status!.status.isNotEmpty
+            ? _status!.status
+            : _statusString;
+        _additional = _status!.additional;
+        _finalized = _status!.finalized;
+        _realTicketId = _status!.realTicketId;
+        _receiptTicketId = _status!.receiptTicketId;
       });
       if (_isTerminal) {
         _pollTimer?.cancel();
@@ -377,38 +388,29 @@ class _ShopInBitCarResearchPaymentViewState
     _pollTimer?.cancel();
 
     final service = ref.read(pShopinBitService);
-    final client = service.client;
 
     try {
-      // Best-effort: the BTCPay webhook is the failsafe that finalizes the fee
-      // and creates the receipt and real car ticket even if this call fails.
-      final logResp = await client.logCarResearchPayment(
-        widget.invoice.btcpayInvoice,
-      );
-
-      if (logResp.hasError || logResp.value == null) {
-        // Payment is confirmed but we could not log it. The webhook will
-        // finalize it server side, so offer the user a shortcut to their
-        // requests where the finalized ticket will appear.
-        await _showFinalizingFallback();
-        return;
-      }
-
-      final result = logResp.value!;
-
-      // log-payment gives us the fee receipt id, which the customer key can't
-      // poll; the real car ticket is a separate id. Find and open it, retrying
-      // for a while since it can take a beat to show up in by-customer. Back
-      // off between tries (2s, 4s, 8s... capped at 15s) so we don't hammer the
-      // by-customer endpoint while we wait.
-      int? realId;
+      // The finalized status usually gives us the real car ticket id (the
+      // customer chat), so open that. It can be null for a bit (sandbox, or
+      // while the ticket is still being created), so fall back to by-customer,
+      // using the receipt id to skip the receipt ticket. The BTCPay webhook
+      // creates the ticket either way.
+      int? realId = _realTicketId;
       const int maxAttempts = 8;
       for (
         int attempt = 0;
         attempt < maxAttempts && realId == null;
         attempt++
       ) {
-        realId = await service.adoptRealCarTicket(result.ticketId);
+        // Re-poll the status first in case the real ticket id has appeared.
+        final statusResp = await service.client.getCarResearchInvoiceStatus(
+          widget.invoice.btcpayInvoice,
+        );
+        realId = statusResp.value?.realTicketId;
+        // Fall back to the by-customer heuristic, excluding the receipt id.
+        realId ??= await service.adoptRealCarTicket(
+          statusResp.value?.receiptTicketId ?? _receiptTicketId ?? 0,
+        );
         if (realId == null && attempt < maxAttempts - 1) {
           final int seconds = (1 << (attempt + 1)).clamp(2, 15).toInt();
           await Future<void>.delayed(Duration(seconds: seconds));
diff --git a/lib/services/shopinbit/shopinbit_service.dart b/lib/services/shopinbit/shopinbit_service.dart
index b9f7a37..0061eca 100644
--- a/lib/services/shopinbit/shopinbit_service.dart
+++ b/lib/services/shopinbit/shopinbit_service.dart
@@ -181,10 +181,14 @@ class ShopInBitService {
     return ref;
   }
 
-  /// log-payment returns the fee *receipt* id, which the customer key can't
-  /// poll (403s). The real car ticket is a separate id that does show up in
-  /// by-customer. Grab the newest ticket we don't already track (not the
-  /// receipt), hydrate just that one, and return its id; null if not there yet.
+  /// Fallback for finding the real car research ticket when the status endpoint
+  /// hasn't populated real_ticket_id yet (sandbox, or briefly while the ticket
+  /// is being created).
+  ///
+  /// The fee receipt id can't be polled by the customer key (403s); the real
+  /// ticket is a separate id that shows up in by-customer. Grab the newest
+  /// ticket we don't already track (not the receipt), hydrate it, and return
+  /// its id, or null if it's not there yet.
   Future<int?> adoptRealCarTicket(int receiptTicketId) async {
     final String key = await ensureCustomerKey();
     final ApiResponse<List<TicketRef>> resp = await _ticketsByCustomer(key);
diff --git a/lib/services/shopinbit/src/client.dart b/lib/services/shopinbit/src/client.dart
index f3909ee..8eb3855 100644
--- a/lib/services/shopinbit/src/client.dart
+++ b/lib/services/shopinbit/src/client.dart
@@ -358,16 +358,20 @@ class ShopInBitClient {
 
   // -- Car Research Fee --
 
+  /// Create the car research fee invoice. Both [billing] and [request] are
+  /// required; without a request the server returns 422 and creates nothing.
+  /// The stored request lets the backend build the customer-facing car ticket
+  /// once the fee is paid.
   Future<ApiResponse<CarResearchInvoice>> createCarResearchInvoice({
     required Address billing,
-    CarResearchRequest? request,
+    required CarResearchRequest request,
   }) async {
     return _request(
       'POST',
       '/car-research/invoice',
       body: {
         'billing': billing.toJson(),
-        if (request != null) 'request': request.toJson(),
+        'request': request.toJson(),
         if (_externalCustomerKey != null)
           'external_customer_key': _externalCustomerKey,
       },
@@ -399,28 +403,16 @@ class ShopInBitClient {
     );
   }
 
-  Future<ApiResponse<Map<String, dynamic>>> getCarResearchInvoiceStatus(
+  /// Poll the car research invoice status. Read-only: it never confirms
+  /// payment. Once [CarResearchInvoiceStatus.finalized] is true the response
+  /// carries the receipt and real ticket references.
+  Future<ApiResponse<CarResearchInvoiceStatus>> getCarResearchInvoiceStatus(
     String invoiceId,
   ) async {
     return _request(
       'GET',
       '/car-research/invoice/$invoiceId/status',
-      parse: (json) => json,
-    );
-  }
-
-  Future<ApiResponse<CarResearchPaymentResult>> logCarResearchPayment(
-    String invoiceId,
-  ) async {
-    return _request(
-      'POST',
-      '/car-research/log-payment',
-      body: {
-        'invoice_id': invoiceId,
-        if (_externalCustomerKey != null)
-          'external_customer_key': _externalCustomerKey,
-      },
-      parse: CarResearchPaymentResult.fromJson,
+      parse: CarResearchInvoiceStatus.fromJson,
     );
   }
 
diff --git a/lib/services/shopinbit/src/models/car_research.dart b/lib/services/shopinbit/src/models/car_research.dart
index 93a1985..8a8a9a7 100644
--- a/lib/services/shopinbit/src/models/car_research.dart
+++ b/lib/services/shopinbit/src/models/car_research.dart
@@ -57,9 +57,12 @@ class CarResearchCurrentInvoice {
   }
 }
 
-/// Whether a car research invoice status counts as paid/finalized per the
-/// ShopinBit 1.0.4 rules: Processing, Settled, or Expired with PaidLate. The
-/// extra lowercase values keep older concierge-style statuses working.
+/// Whether a car research invoice status counts as paid/finalized.
+///
+/// Prefer the `finalized` boolean from the status endpoint (see
+/// [CarResearchInvoiceStatus.finalized]). This is the fallback for the raw
+/// status/additional strings: Processing, Settled, or Expired with PaidLate,
+/// plus lowercase values for older concierge-style statuses.
 bool carResearchIsFinalized(String? status, String? additional) {
   final s = (status ?? '').toLowerCase().trim();
   final a = (additional ?? '').toLowerCase().trim();
@@ -100,25 +103,56 @@ class CarResearchInvoice {
   }
 }
 
-class CarResearchPaymentResult {
+/// Result of GET /car-research/invoice/{invoice_id}/status.
+///
+/// Read-only: it never confirms payment, so poll until [finalized] is true.
+/// Once finalized it carries the created ticket references:
+///
+/// * [realTicketId] / [realTicketNumber]: the customer-facing car research
+///   chat. Open this for the customer after payment.
+/// * [receiptTicketId] / [receiptTicketNumber]: the paid-fee receipt only;
+///   do NOT use it as the active customer chat.
+///
+/// The sandbox populates only the receipt references and leaves the real ticket
+/// fields null, so [realTicketId] is nullable.
+class CarResearchInvoiceStatus {
   final String status;
-  final int ticketId;
-  final String ticketNumber;
-  final String externalCustomerKey;
+  final String? additional;
+  final bool finalized;
+  final int? receiptTicketId;
+  final String? receiptTicketNumber;
+  final int? realTicketId;
+  final String? realTicketNumber;
+  final String? externalCustomerKey;
 
-  CarResearchPaymentResult({
+  CarResearchInvoiceStatus({
     required this.status,
-    required this.ticketId,
-    required this.ticketNumber,
-    required this.externalCustomerKey,
+    this.additional,
+    required this.finalized,
+    this.receiptTicketId,
+    this.receiptTicketNumber,
+    this.realTicketId,
+    this.realTicketNumber,
+    this.externalCustomerKey,
   });
 
-  factory CarResearchPaymentResult.fromJson(Map<String, dynamic> json) {
-    return CarResearchPaymentResult(
-      status: json['status'] as String,
-      ticketId: int.tryParse(json['ticket_id'].toString()) ?? 0,
-      ticketNumber: json['ticket_number'] as String,
-      externalCustomerKey: json['external_customer_key'] as String,
+  factory CarResearchInvoiceStatus.fromJson(Map<String, dynamic> json) {
+    int? toIntOrNull(dynamic v) {
+      if (v == null) return null;
+      if (v is int) return v;
+      if (v is double) return v.toInt();
+      return int.tryParse(v.toString());
+    }
+
+    return CarResearchInvoiceStatus(
+      status: json['status']?.toString() ?? '',
+      additional: json['additional']?.toString(),
+      finalized: json['finalized'] == true,
+      receiptTicketId: toIntOrNull(json['receipt_ticket_id']),
+      receiptTicketNumber: json['receipt_ticket_number']?.toString(),
+      realTicketId: toIntOrNull(json['real_ticket_id']),
+      realTicketNumber: json['real_ticket_number']?.toString(),
+      externalCustomerKey: json['external_customer_key']?.toString(),
     );
   }
 }