feat(spl): add mock SolanaTokenWallet impl

diff --git a/lib/wallets/wallet/impl/sub_wallets/solana_token_wallet.dart b/lib/wallets/wallet/impl/sub_wallets/solana_token_wallet.dart
new file mode 100644
index 0000000..b0bcb60
--- /dev/null
+++ b/lib/wallets/wallet/impl/sub_wallets/solana_token_wallet.dart
@@ -0,0 +1,118 @@
+/*
+ * This file is part of Stack Wallet.
+ *
+ * Copyright (c) 2025 Cypher Stack
+ * All Rights Reserved.
+ * The code is distributed under GPLv3 license, see LICENSE file for details.
+ *
+ */
+
+import 'package:isar_community/isar.dart';
+
+import '../../../../models/paymint/fee_object_model.dart';
+import '../../../../utilities/amount/amount.dart';
+import '../../../crypto_currency/crypto_currency.dart';
+import '../../../models/tx_data.dart';
+import '../../wallet.dart';
+
+/// Mock Solana Token Wallet for UI development.
+///
+/// TODO: Complete implementation with real balance fetching, transaction
+/// handling, and fee estimation when SolanaAPI is ready.
+class SolanaTokenWallet extends Wallet {
+  /// Mock wallet for testing UI.
+  SolanaTokenWallet({
+    required this.tokenMint,
+    required this.tokenName,
+    required this.tokenSymbol,
+    required this.tokenDecimals,
+  }) : super(Solana(CryptoCurrencyNetwork.main)); // TODO: make testnet-capable.
+
+  final String tokenMint;
+  final String tokenName;
+  final String tokenSymbol;
+  final int tokenDecimals;
+
+  // =========================================================================
+  // Abstract method implementations
+  // =========================================================================
+
+  @override
+  FilterOperation? get changeAddressFilterOperation => null;
+
+  @override
+  FilterOperation? get receivingAddressFilterOperation => null;
+
+  @override
+  Future<void> init() async {
+    await super.init();
+    // TODO: Initialize token account address derivation.
+    await Future<void>.delayed(const Duration(milliseconds: 100));
+  }
+
+  @override
+  Future<TxData> prepareSend({required TxData txData}) async {
+    // TODO: Build SPL token transfer instruction.
+    throw UnimplementedError("prepareSend not yet implemented");
+  }
+
+  @override
+  Future<TxData> confirmSend({required TxData txData}) async {
+    // TODO: Sign and broadcast SPL token transfer.
+    throw UnimplementedError("confirmSend not yet implemented");
+  }
+
+  @override
+  Future<void> recover({required bool isRescan}) async {
+    // TODO.
+  }
+
+  @override
+  Future<void> updateNode() async {
+    // No-op for token wallet.
+  }
+
+  @override
+  Future<void> updateTransactions() async {
+    // TODO: Fetch token transfer history from Solana RPC.
+  }
+
+  @override
+  Future<void> updateBalance() async {
+    // TODO: Fetch token balance from Solana RPC.
+  }
+
+  @override
+  Future<bool> updateUTXOs() async {
+    // Not applicable for Solana tokens.
+    return true;
+  }
+
+  @override
+  Future<void> updateChainHeight() async {
+    // TODO: Get latest Solana block height.
+  }
+
+  @override
+  Future<Amount> estimateFeeFor(Amount amount, BigInt feeRate) async {
+    // Mock fee estimation: 5000 lamports for token transfer.
+    return Amount.zeroWith(fractionDigits: tokenDecimals);
+  }
+
+  @override
+  Future<FeeObject> get fees async {
+    // TODO: Return real Solana fee estimates.
+    throw UnimplementedError("fees not yet implemented");
+  }
+
+  @override
+  Future<bool> pingCheck() async {
+    // TODO: Check Solana RPC connection.
+    return true;
+  }
+
+  @override
+  Future<void> checkSaveInitialReceivingAddress() async {
+    // Token accounts are derived, not managed separately.
+  }
+}