feat(delivery): complete MySQL version-to-package mapping

- 8.0 from Ubuntu archive, 8.4 from MySQL official APT repo
- 5.6/5.7 not supported for now; enforce one MySQL series per host
- Sync Go version whitelist with the playbook package map

server/internal/service/delivery.go

@@ -286,8 +286,9 @@ func (s *DeliveryService) CreateTask(ctx context.Context, userID uint64, isAdmin
 	return &task, false, nil
 }
 
-// 版本白名单与 playbook 的 mysql_package_map 保持同步。
-var supportedMySQLVersions = map[string]bool{"8.0": true}
+// 版本白名单与 playbook 的 mysql_package_map 保持同步：
+// 8.0 走 Ubuntu 自带源，8.4 走 MySQL 官方 APT 源；5.6/5.7 已 EOL 且无 noble 包，不支持。
+var supportedMySQLVersions = map[string]bool{"8.0": true, "8.4": true}
 
 // 拓扑白名单：playbook 已支持 primary_replica/mgr_3 的配置渲染，
 // 但调度器仍是单主机模型且复制编排未自动化，本期仅放开 standalone。
@@ -319,7 +320,7 @@ func validateDeliveryInput(input MySQLDeliveryInput, dataDisks []string) error {
 		return fmt.Errorf("requested resources are outside the supported range (memory: 2048-65536 MiB, storage: 20-2000 GiB)")
 	}
 	if input.MySQLVersion != "" && !supportedMySQLVersions[input.MySQLVersion] {
-		return fmt.Errorf("unsupported mysql_version %q, supported: 8.0", input.MySQLVersion)
+		return fmt.Errorf("unsupported mysql_version %q, supported: 8.0, 8.4 (5.6/5.7 are EOL and have no Ubuntu 24.04 packages)", input.MySQLVersion)
 	}
 	if input.Topology != "" && !supportedTopologies[input.Topology] {
 		return fmt.Errorf("unsupported topology %q, supported: standalone (primary_replica/mgr_3 pending scheduler support)", input.Topology)