feat(spl): add Solana token (SPL) state mgmt providers

diff --git a/lib/wallets/isar/providers/solana/current_sol_token_wallet_provider.dart b/lib/wallets/isar/providers/solana/current_sol_token_wallet_provider.dart
new file mode 100644
index 0000000..ab17451
--- /dev/null
+++ b/lib/wallets/isar/providers/solana/current_sol_token_wallet_provider.dart
@@ -0,0 +1,15 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../../../wallet/impl/sub_wallets/solana_token_wallet.dart';
+
+/// State provider for the currently active Solana token wallet.
+/// 
+/// This allows global tracking of which token wallet is being viewed/interacted-with.
+final solanaTokenServiceStateProvider =
+    StateProvider<SolanaTokenWallet?>((ref) => null);
+
+/// Public provider to read the current active Solana token wallet.
+/// 
+/// Use this in UI widgets to get the active token wallet.
+final pCurrentSolanaTokenWallet =
+    Provider<SolanaTokenWallet?>((ref) => ref.watch(solanaTokenServiceStateProvider));
diff --git a/lib/wallets/isar/providers/solana/sol_token_balance_provider.dart b/lib/wallets/isar/providers/solana/sol_token_balance_provider.dart
new file mode 100644
index 0000000..30b0691
--- /dev/null
+++ b/lib/wallets/isar/providers/solana/sol_token_balance_provider.dart
@@ -0,0 +1,32 @@
+import 'package:decimal/decimal.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../../../../models/balance.dart';
+import '../../../../utilities/amount/amount.dart';
+
+/// Provider family for Solana token balance.
+/// 
+/// Currently returns mock data while API is a WIP.
+///
+/// Example usage in UI:
+///   final balance = ref.watch(
+///     pSolanaTokenBalance((walletId: 'wallet1', tokenMint: 'EPjFWaJUwYUoRwzwkH4H8gNB7zHW9tLT6NCKB8S4yh6h'))
+///   );
+final pSolanaTokenBalance = Provider.family<
+    Balance,
+    ({String walletId, String tokenMint})>((ref, params) {
+  // Mock data for UI development.
+  // TODO: when API is ready, this should fetch real balance from SolanaAPI.
+  return Balance(
+    total: Amount.fromDecimal(
+      Decimal.parse("1000.00"),
+      fractionDigits: 6,
+    ),
+    spendable: Amount.fromDecimal(
+      Decimal.parse("1000.00"),
+      fractionDigits: 6,
+    ),
+    blockedTotal: Amount.zeroWith(fractionDigits: 6),
+    pendingSpendable: Amount.zeroWith(fractionDigits: 6),
+  );
+});