feat: enhance agent management and validation logic

- Updated AGENTS.md to clarify agent account restrictions and permissions.
- Implemented checks in AgentNodeAdminUserStoreController and AgentNodeRoleStoreController to restrict admin user and role creation to the agent's own node.
- Enhanced validation in AdminPlayerStoreController and AdminPlayerUpdateController to enforce credit limit and rebate rate rules based on player funding mode.
- Refactored various request classes to utilize shared admin account field rules for consistency.
- Improved error handling in services related to credit allocation and rebate limits to ensure proper validation and messaging.

app/Http/Controllers/Api/V1/Admin/AgentSettlement/AdminCreditLedgerIndexController.php

@@ -29,11 +29,11 @@ final class AdminCreditLedgerIndexController extends Controller
         abort_if($admin === null, 401);
 
         $adminSiteId = (int) $request->query('admin_site_id', 0);
-        abort_if($adminSiteId <= 0, 422, 'admin_site_id required');
+        abort_if($adminSiteId <= 0, 422, 'admin.admin_site_id_required');
         abort_if(! AdminAgentSettlementScope::siteAccessible($admin, $adminSiteId), 403);
 
         $siteCode = (string) DB::table('admin_sites')->where('id', $adminSiteId)->value('code');
-        abort_if($siteCode === '', 422, 'admin_site not found');
+        abort_if($siteCode === '', 422, 'admin.admin_site_not_found');
 
         $periodId = (int) $request->query('settlement_period_id', 0);
         if ($periodId > 0) {