feat: 添加货币组至设置控制器并更新测试用例

- 在 SettingIndexController 中新增 'currency' 组，以支持货币相关设置。
- 更新 PublicSettingsApiTest，新增测试用例以验证货币组的返回数据，确保 API 正确处理货币设置。

app/Http/Controllers/Api/V1/Setting/SettingIndexController.php

@@ -17,6 +17,7 @@ final class SettingIndexController extends Controller
     /** @var list<string> */
     private const PUBLIC_GROUPS = [
         'frontend',
+        'currency',
     ];
 
     public function __invoke(Request $request): JsonResponse

tests/Feature/PublicSettingsApiTest.php

@@ -20,6 +20,22 @@ test('public settings requires allowed group', function (): void {
         ->assertJsonPath('code', ErrorCode::ClientHttpError->value);
 });
 
+test('public settings returns currency group', function (): void {
+    \App\Models\LotterySetting::query()->updateOrCreate(
+        ['setting_key' => 'currency.display_decimals'],
+        [
+            'group_name' => 'currency',
+            'value_json' => 3,
+            'description_zh' => '展示小数位',
+        ],
+    );
+
+    $this->getJson('/api/v1/settings?group=currency')
+        ->assertOk()
+        ->assertJsonPath('code', ErrorCode::Success->value)
+        ->assertJsonFragment(['key' => 'currency.display_decimals', 'value' => 3]);
+});
+
 test('public settings returns frontend group only', function (): void {
     \App\Models\LotterySetting::query()->updateOrCreate(
         ['setting_key' => 'frontend.play_rules_html_zh'],