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/Services/AgentSettlement/SettlementPaymentService.php

@@ -39,7 +39,14 @@ final class SettlementPaymentService
                 ]);
             }
 
-            $payAmount = min($amount, abs((int) $bill->unpaid_amount));
+            $unpaid = abs((int) $bill->unpaid_amount);
+            if ($amount > $unpaid) {
+                throw ValidationException::withMessages([
+                    'amount' => ['exceeds_unpaid'],
+                ]);
+            }
+
+            $payAmount = $amount;
             if ($payAmount <= 0) {
                 return;
             }