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/Support/AgentAdminUserAuthorization.php

@@ -15,7 +15,15 @@ final class AgentAdminUserAuthorization
 
         $agent = $target->primaryAgentNode();
         if ($agent === null) {
-            return false;
+            // Target is a platform account (site admin)
+            // Check if admin can access the same sites
+            $adminSiteIds = $admin->accessibleAdminSiteIds();
+            $targetSiteIds = $target->accessibleAdminSiteIds();
+            if ($adminSiteIds === null || $targetSiteIds === null) {
+                return false;
+            }
+            // Check if they share any accessible sites
+            return !empty(array_intersect($adminSiteIds, $targetSiteIds));
         }
 
         return AdminAgentScope::nodeVisibleTo($admin, $agent);
@@ -36,8 +44,13 @@ final class AgentAdminUserAuthorization
         }
 
         $agent = $target->primaryAgentNode();
+        if ($agent === null) {
+            // Target is a platform account (site admin)
+            // Platform accounts can manage other platform accounts in the same site
+            return true;
+        }
 
-        return $agent !== null && AdminAgentScope::nodeManageableBy($admin, $agent);
+        return AdminAgentScope::nodeManageableBy($admin, $agent);
     }
 
     public static function denyUnlessUserManageable(AdminUser $admin, AdminUser $target): ?\Illuminate\Http\JsonResponse