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/api/modules/icons.js

@@ -0,0 +1,8 @@
+/**
+ * Icon catalog API — serves the universal icon picker (FA5 + sprite + custom).
+ */
+export const iconsApiMethods = {
+  getIconCatalog() {
+    return this.request('/icons/catalog')
+  },
+}