feat(admin): back the SPA icon picker with the server catalog

FaIconPicker drops its duplicated hard-coded FA subset and loads
GET /aksrt/v1/icons/catalog: full solid/regular/brands sets, the
built-in zibsvg sprite tab and an inline custom SVG tab. Props/emit
surface is unchanged; the system-notice title icon schema drift
(input vs icon) is fixed on the JS side.

assets/admin/src/schema/sections/global/system-notice.js

@@ -124,7 +124,7 @@ export const systemNoticeSchema = {
         },
         { key: 'system_notice_radius', label: '按钮圆角', type: 'switch', default: false, dependsOn: { key: 'system_notice_enabled', value: true }, help: '开启后弹窗按钮使用圆角样式' },
         { key: 'system_notice_class', label: '公告样式类', type: 'input', default: '', dependsOn: { key: 'system_notice_enabled', value: true } },
-        { key: 'system_notice_title_icon', label: '标题图标', type: 'input', default: '', dependsOn: { key: 'system_notice_enabled', value: true }, help: '如 fa fas fa-bullhorn' },
+        { key: 'system_notice_title_icon', label: '标题图标', type: 'icon', default: '', dependsOn: { key: 'system_notice_enabled', value: true } },
         { key: 'system_notice_title_class', label: '标题背景配色', type: 'select', default: '', dependsOn: { key: 'system_notice_enabled', value: true }, options: [
           { label: '无', value: '' },
           { label: '炫彩黄', value: 'jb-yellow' },