refactor(horizon): 移除管理员通知并简化主题初始化逻辑

- 删除了管理员使用Horizon主题时的全局通知功能
- 移除了主题ID获取和URL构建相关代码
- 简化了API初始化器中的条件判断逻辑
- 保留了实验性屏幕组件和用户颜色选择器的渲染功能

javascripts/discourse/api-initializers/horizon.gjs

@@ -1,26 +1,8 @@
-import { addGlobalNotice } from "discourse/components/global-notice";
 import { apiInitializer } from "discourse/lib/api";
-import getURL from "discourse/lib/get-url";
-import { currentThemeId } from "discourse/lib/theme-selector";
 import ExperimentalScreen from "../components/experimental-screen";
 import UserColorPaletteSelector from "../components/user-color-palette-selector";
 
 export default apiInitializer("1.8.0", (api) => {
-  if (api.getCurrentUser()?.admin) {
-    const themeId = currentThemeId();
-    const themeURL = getURL(`/admin/customize/themes/${themeId}`);
-    const horizonThemeUrl = getURL(`/admin/customize/themes/-2`);
-    addGlobalNotice(
-      `<b>Admin notice:</b> you are using the <em>Horizon (beta)</em> theme. This theme is now installed automatically in Discourse core. You should <a href="${themeURL}">uninstall this theme</a>, and reconfigure the <a href="${horizonThemeUrl}">preinstalled Horizon theme</a>.`,
-      "loading-slider-theme",
-      {
-        dismissable: true,
-        level: "warn",
-        dismissDuration: moment.duration("1", "hour"),
-      }
-    );
-  }
-
   api.renderInOutlet("above-main-container", ExperimentalScreen);
   api.renderInOutlet("sidebar-footer-actions", UserColorPaletteSelector);