refactor：拆分 API 路由与请求校验，统一 final 类和代码风格

app/Http/Controllers/Api/V1/Wallet/WalletBalanceController.php

@@ -2,13 +2,14 @@
 
 namespace App\Http\Controllers\Api\V1\Wallet;
 
-use App\Http\Controllers\Controller;
-use App\Lottery\ErrorCode;
 use App\Models\Player;
+use App\Lottery\ErrorCode;
 use App\Models\PlayerWallet;
 use App\Support\ApiResponse;
-use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Request;
+use App\Support\CurrencyResolver;
+use Illuminate\Http\JsonResponse;
+use App\Http\Controllers\Controller;
 
 /**
  * 【玩家】查询彩票侧钱包余额。
@@ -22,7 +23,7 @@ use Illuminate\Http\Request;
  * - `available_balance`：`balance - frozen_balance`，表示当前可用于下注的整数最小货币单位（不为负）
  * - `main_balance`：主站钱包余额占位，接入主站 API 后再返回实数；当前固定 `null`
  */
-class WalletBalanceController extends Controller
+final class WalletBalanceController extends Controller
 {
     private const WALLET_TYPE_LOTTERY = 'lottery';
 
@@ -68,16 +69,9 @@ class WalletBalanceController extends Controller
      */
     private function resolveCurrencyCode(Request $request, Player $player): string|JsonResponse
     {
-        $raw = $request->query('currency');
-        if (is_string($raw) && $raw !== '') {
-            $code = strtoupper(substr(trim($raw), 0, 16));
-        } else {
-            $fallback = $player->default_currency ?? config('lottery.default_currency', 'NPR');
-            $code = strtoupper(substr(trim((string) $fallback), 0, 16));
-        }
+        $code = CurrencyResolver::resolve($request, $player, 'currency');
 
-        // 币种码：字母数字，长度 1–16，与 migrations 字段一致
-        if (! preg_match('/^[A-Z0-9]{1,16}$/', $code)) {
+        if (! CurrencyResolver::isValid($code)) {
             return ApiResponse::error(
                 __('wallet.invalid_currency'),
                 ErrorCode::WalletInvalidCurrency->value,