fix: use locale-aware parsing for buy amount and eth fee inputs

Parse the buy form fiat/crypto amount and the eth fee gwei and gas limit
fields with the active locale's decimal and group separators instead of
hardcoded comma stripping, which mis-scaled values in comma-decimal locales.

Author: sneurlax

lib/pages/buy_view/buy_form.dart

@@ -31,6 +31,8 @@ import '../../services/buy/buy_response.dart';
 import '../../services/buy/simplex/simplex_api.dart';
 import '../../themes/stack_colors.dart';
 import '../../utilities/address_utils.dart';
+import '../../utilities/amount/amount.dart';
+import '../../utilities/amount/amount_formatter.dart';
 import '../../utilities/assets.dart';
 import '../../utilities/barcode_scanner_interface.dart';
 import '../../utilities/clipboard_interface.dart';
@@ -124,6 +126,30 @@ class _BuyFormState extends ConsumerState<BuyForm> {
   // static Decimal maxCrypto = Decimal.parse((10000.00000000).toString());
   // static String boundedCryptoTicker = '';
 
+  /// Parse a buy amount string using the active locale's decimal and group
+  /// separators. Fiat amounts are parsed via [Amount.tryParseFiatString];
+  /// crypto amounts reuse the locale-aware [pAmountFormatter] parser so that
+  /// full crypto precision is preserved.
+  Decimal? _tryParseBuyAmount(String value) {
+    if (buyWithFiat) {
+      return Amount.tryParseFiatString(
+        value,
+        locale: ref.read(localeServiceChangeNotifierProvider).locale,
+      )?.decimal;
+    }
+
+    final cc = coin;
+    if (cc != null) {
+      return ref.read(pAmountFormatter(cc)).tryParse(value)?.decimal;
+    }
+
+    // Fall back to fiat-style locale parsing when no coin is available.
+    return Amount.tryParseFiatString(
+      value,
+      locale: ref.read(localeServiceChangeNotifierProvider).locale,
+    )?.decimal;
+  }
+
   String _amountOutOfRangeErrorString = "";
   void validateAmount() {
     if (_buyAmountController.text.isEmpty) {
@@ -133,7 +159,7 @@ class _BuyFormState extends ConsumerState<BuyForm> {
       return;
     }
 
-    final value = Decimal.tryParse(_buyAmountController.text);
+    final value = _tryParseBuyAmount(_buyAmountController.text);
     if (value == null) {
       setState(() {
         _amountOutOfRangeErrorString = "Invalid amount";
@@ -414,11 +440,12 @@ class _BuyFormState extends ConsumerState<BuyForm> {
       crypto: selectedCrypto!,
       fiat: selectedFiat!,
       youPayFiatPrice: buyWithFiat
-          ? Decimal.parse(_buyAmountController.text)
+          ? (_tryParseBuyAmount(_buyAmountController.text) ?? Decimal.zero)
           : Decimal.parse("100"), // dummy value
       youReceiveCryptoAmount: buyWithFiat
           ? Decimal.parse("0.000420282") // dummy value
-          : Decimal.parse(_buyAmountController.text), // Ternary for this
+          : (_tryParseBuyAmount(_buyAmountController.text) ??
+                Decimal.zero), // Ternary for this
       id: "id", // anything; we get an ID back
       receivingAddress: _receiveAddressController.text,
       buyWithFiat: buyWithFiat,
@@ -1123,12 +1150,23 @@ class _BuyFormState extends ConsumerState<BuyForm> {
                                   final ClipboardData? data = await clipboard
                                       .getData(Clipboard.kTextPlain);
 
-                                  final amountString = Decimal.tryParse(
+                                  final amountString = _tryParseBuyAmount(
                                     data?.text ?? "",
                                   );
                                   if (amountString != null) {
+                                    final locale = ref
+                                        .read(
+                                          localeServiceChangeNotifierProvider,
+                                        )
+                                        .locale;
+                                    final decimalSeparator =
+                                        Util.getSymbolsFor(
+                                          locale: locale,
+                                        )?.DECIMAL_SEP ??
+                                        ".";
                                     _buyAmountController.text = amountString
-                                        .toString();
+                                        .toString()
+                                        .replaceFirst(".", decimalSeparator);
 
                                     validateAmount();
                                   }

lib/widgets/eth_fee_form.dart

@@ -2,7 +2,9 @@ import 'dart:async';
 
 import 'package:decimal/decimal.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import '../providers/global/locale_provider.dart';
 import '../services/ethereum/ethereum_api.dart';
 import '../themes/stack_colors.dart';
 import '../utilities/constants.dart';
@@ -35,7 +37,7 @@ class EthEIP1559Fee {
       "gasLimit: $gasLimit)";
 }
 
-class EthFeeForm extends StatefulWidget {
+class EthFeeForm extends ConsumerStatefulWidget {
   EthFeeForm({
     super.key,
     this.minGasLimit = 21000,
@@ -56,10 +58,10 @@ class EthFeeForm extends StatefulWidget {
   final void Function(EthEIP1559Fee) stateChanged;
 
   @override
-  State<EthFeeForm> createState() => _EthFeeFormState();
+  ConsumerState<EthFeeForm> createState() => _EthFeeFormState();
 }
 
-class _EthFeeFormState extends State<EthFeeForm> {
+class _EthFeeFormState extends ConsumerState<EthFeeForm> {
   static const _textFadeDuration = Duration(milliseconds: 300);
 
   final maxBaseController = TextEditingController();
@@ -71,11 +73,29 @@ class _EthFeeFormState extends State<EthFeeForm> {
 
   late int _gasLimitCache;
 
+  /// Normalize a numeric input string using the active locale's decimal and
+  /// group separators so that it can be parsed by [Decimal]/[int], which only
+  /// understand a "." decimal point and no group separators. This preserves
+  /// full precision (gwei needs up to 9 decimal places).
+  String _normalizeForParsing(String value) {
+    final locale = ref.read(localeServiceChangeNotifierProvider).locale;
+    final numberSymbols = Util.getSymbolsFor(locale: locale);
+    final groupSeparator = numberSymbols?.GROUP_SEP ?? ",";
+    final decimalSeparator = numberSymbols?.DECIMAL_SEP ?? ".";
+
+    return value
+        .replaceAll(groupSeparator, "")
+        .replaceFirst(decimalSeparator, ".");
+  }
+
   EthEIP1559Fee get _current => EthEIP1559Fee(
-    maxBaseFeeGwei: Decimal.tryParse(maxBaseController.text) ?? Decimal.zero,
+    maxBaseFeeGwei:
+        Decimal.tryParse(_normalizeForParsing(maxBaseController.text)) ??
+        Decimal.zero,
     priorityFeeGwei:
-        Decimal.tryParse(priorityFeeController.text) ?? Decimal.zero,
-    gasLimit: int.parse(gasLimitController.text),
+        Decimal.tryParse(_normalizeForParsing(priorityFeeController.text)) ??
+        Decimal.zero,
+    gasLimit: int.parse(_normalizeForParsing(gasLimitController.text)),
   );
 
   String _currentBase = "Current: ";
@@ -267,7 +287,7 @@ class _EthFeeFormState extends State<EthFeeForm> {
             keyboardType: const TextInputType.numberWithOptions(decimal: true),
             focusNode: gasLimitFocus,
             onChanged: (value) {
-              final intValue = int.tryParse(value);
+              final intValue = int.tryParse(_normalizeForParsing(value));
               if (intValue == null ||
                   intValue < widget.minGasLimit ||
                   intValue > widget.maxGasLimit) {