refactor(admin): retire settings migration and compat menu demotion

Stop auto-running AKSRT_Settings_Migration, drop multi-option settings
merge and Zibll favicon aliases, remove the migration tools entry from
menus/schema, flatten admin sections so pages are not demoted into a
compat bag, and retire the migration-status payload for leftover SPA
routes after a full admin rebuild.

assets/admin/src/constants/sections/tools.js

@@ -2,7 +2,7 @@ import { renderFaIcon, customPage, schemaPage } from './helpers'
 
 export const toolsSection = {
   key: 'tools-compat',
-  label: '兼容&工具',
+  label: '工具',
   icon: renderFaIcon('fas fa-toolbox'),
   route: '/tools',
   children: [
@@ -34,15 +34,6 @@ export const toolsSection = {
       desc: '查看主题环境、数据表、邮箱验证迁移和系统诊断状态。',
       component: 'ToolsHealth',
     }),
-    customPage({
-      key: 'tools-migration',
-      name: 'ToolsMigration',
-      label: '迁移状态',
-      route: '/tools/migration',
-      title: '迁移状态',
-      desc: '查看数据库 schema 版本、设置迁移版本和迁移日志。',
-      component: 'ToolsMigration',
-    }),
     customPage({
       key: 'tools-email-rollback',
       name: 'ToolsEmailRollback',