fix(admin): route homepage settings to custom HomepageSettings page

The page-display homepage menu entry was registered as a SchemaPage for
section "homepage", but PHP's page_display schema has no such section, so
GET /wp-json/aksrt/v1/settings/schema/page_display/homepage returned 404
(未知的设置分组: homepage). Point the route at HomepageSettings, which
already uses /settings/homepage like FooterSettings.

assets/admin/src/constants/sections/page-display.js

@@ -55,15 +55,14 @@ export const pageDisplaySection = {
       desc: '页脚布局、友链、版权信息配置。',
       component: 'FooterSettings',
     }),
-    schemaPage({
+    customPage({
       key: 'page-display-homepage',
       name: 'PageDisplayHomepage',
       label: '首页配置',
       route: '/page-display/homepage',
       title: '首页配置',
       desc: '首页内容模型、主列表、分类 Tab 与首页交互配置。',
-      canonicalDomain: 'page_display',
+      component: 'HomepageSettings',
-      section: 'homepage',
     }),
     schemaPage({
       key: 'page-display-float-btn',