fix(core) : RBAC review fixes - code readonly in edit, TOCTOU doc, canManage reactive, itemsPerPage 999

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/modules/core/pages/admin/roles.vue

@@ -81,7 +81,7 @@ import type { Role } from '~/shared/types/rbac'
 const { t } = useI18n()
 const api = useApi()
 const { can } = usePermissions()
-const canManage = can('core.roles.manage')
+const canManage = computed(() => can('core.roles.manage'))
 
 useHead({ title: t('admin.roles.title') })