Add QR restore

diff --git a/lib/screens/restore_wallet.dart b/lib/screens/restore_wallet.dart
index 5989ec9..b82b989 100644
--- a/lib/screens/restore_wallet.dart
+++ b/lib/screens/restore_wallet.dart
@@ -11,11 +11,11 @@ import 'package:polyseed/polyseed.dart';
 import 'package:skylight_wallet/l10n/app_localizations.dart';
 import 'package:skylight_wallet/models/fiat_rate_model.dart';
 import 'package:skylight_wallet/util/get_height_by_date.dart';
-import 'package:skylight_wallet/util/restore_qr.dart';
 import 'package:skylight_wallet/util/secure_screen.dart';
 import 'package:skylight_wallet/util/logging.dart';
 import 'package:skylight_wallet/wallet_core_glue.dart';
 import 'package:skylight_wallet/widgets/ui/ui.dart';
+import 'package:wallet_domain/wallet_domain.dart' show parseRestoreQr;
 
 class RestoreWalletScreen extends StatefulWidget {
   const RestoreWalletScreen({super.key});
diff --git a/lib/screens/send.dart b/lib/screens/send.dart
index 0d667cc..8395c48 100644
--- a/lib/screens/send.dart
+++ b/lib/screens/send.dart
@@ -361,6 +361,12 @@ class _SendScreenState extends State<SendScreen> {
         });
       }
     } catch (error) {
+      // Let the same address+amount be asked again. The key is claimed before
+      // the work starts, so without this a single failure pins the fee at '—'
+      // for that pair forever: every later revalidation matches the key and
+      // returns early, and only editing the address or amount can clear it.
+      _lastFeeFetchKey = '';
+
       // Only update state if this is still the latest request
       if (currentRequest == _feeCalculationCounter && mounted) {
         setState(() {
@@ -544,7 +550,7 @@ class _SendScreenState extends State<SendScreen> {
 
   void _setBalanceAsSendAmount() {
     final wallet = appWalletOf(context);
-    _amountController.text = (wallet.unlockedBalance ?? 0).toString();
+    _amountController.text = _plainAmount(wallet.unlockedBalance ?? 0);
 
     setState(() {
       _isSweepAll = true;
@@ -691,6 +697,24 @@ class _SendScreenState extends State<SendScreen> {
 /// Monero is decimal-12; cap the displayed amount for legibility.
 String _amountText(double amount) => amount.toStringAsFixed(5);
 
+/// Monero's decimal places. Matches the adapter's own constant; kept local so
+/// this file does not reach into the adapter's privates.
+const _xmrDecimals = 12;
+
+/// [amount] as a plain decimal, never exponential.
+///
+/// `double.toString()` switches to exponential notation below 1e-6 -- a
+/// 500000-piconero balance renders as "5e-7". `decimalToBaseUnits` splits on
+/// '.' and hands the rest to `BigInt.parse`, which throws on an exponent, so
+/// the fee estimate fails and the field cannot be sent. Only the Max button
+/// fills this field from a raw double, which is why it only broke there.
+String _plainAmount(double amount) {
+  final fixed = amount.toStringAsFixed(_xmrDecimals);
+  if (!fixed.contains('.')) return fixed;
+  final trimmed = fixed.replaceFirst(RegExp(r'0+$'), '');
+  return trimmed.endsWith('.') ? trimmed.substring(0, trimmed.length - 1) : trimmed;
+}
+
 /// `abcd…wxyz`: keeps [head] leading and [tail] trailing chars of a long
 /// address, eliding the middle. Returns the string unchanged when short.
 String _shortenMiddle(String value, {required int head, required int tail}) {
diff --git a/lib/util/restore_qr.dart b/lib/util/restore_qr.dart
deleted file mode 100644
index 0b53ed8..0000000
--- a/lib/util/restore_qr.dart
+++ /dev/null
@@ -1,60 +0,0 @@
-/// Parses restore QR payloads. Accepts the URI format
-/// (`monero:`, `monero-wallet:` or `monero_wallet:` with `seed`/`height` query
-/// params) as well as a bare seed phrase.
-library;
-
-const _moneroRestoreSchemes = {'monero', 'monero-wallet', 'monero_wallet'};
-
-class ParsedRestoreQr {
-  final String seed;
-  final int? restoreHeight;
-
-  const ParsedRestoreQr({required this.seed, this.restoreHeight});
-}
-
-ParsedRestoreQr? parseRestoreQr(String raw) {
-  final code = raw.trim();
-  if (code.isEmpty) return null;
-
-  final colon = code.indexOf(':');
-  if (colon > 0) {
-    final scheme = code.substring(0, colon).toLowerCase();
-    if (_moneroRestoreSchemes.contains(scheme)) {
-      final query = code.substring(colon + 1).replaceAll('?', '&');
-      final params = _parseQuery(query);
-      final seed = (params['seed'] ?? '').trim();
-      if (seed.isEmpty) return null;
-      final heightStr = params['height'] ?? params['restoreHeight'];
-      final height = heightStr != null ? int.tryParse(heightStr.trim()) : null;
-      return ParsedRestoreQr(seed: seed, restoreHeight: height);
-    }
-  }
-
-  // Not a recognized URI — treat the whole payload as a seed phrase.
-  return ParsedRestoreQr(seed: code);
-}
-
-/// Builds a restore payload (`monero_wallet:?seed=...&height=...`)
-/// for encoding into a QR code. The seed is URL-encoded so spaces survive.
-String buildRestoreQr({required String seed, int? height}) {
-  final buffer = StringBuffer('monero_wallet:?seed=${Uri.encodeQueryComponent(seed)}');
-  if (height != null) buffer.write('&height=$height');
-  return buffer.toString();
-}
-
-Map<String, String> _parseQuery(String query) {
-  final result = <String, String>{};
-  for (final pair in query.split('&')) {
-    if (pair.isEmpty) continue;
-    final eq = pair.indexOf('=');
-    if (eq < 0) continue;
-    final key = pair.substring(0, eq);
-    final value = pair.substring(eq + 1);
-    try {
-      result[key] = Uri.decodeQueryComponent(value);
-    } catch (_) {
-      result[key] = value;
-    }
-  }
-  return result;
-}