FA5's own single-class declarations lose the cascade to the later
.fa,.far,.fas family rule, so zibll-legacy values like "fa fab fa-weixin"
rendered with the Free font and came up blank — visible in the picker's
brand tab (500px…zhihu) and on every brand icon in the SPA and frontend
social links. Re-assert .fa.fab (and .fa.far weight) in the three
stylesheets that load FA5. Also remove the empty aksrt_svgs['qqww']
sprite entry, which surfaced as a blank built-in SVG item.
Mirror the reference theme's universal picker on FA5: a generated full
catalog of the bundled FA5 Free 5.15.4 fonts (src/Icons/fa5-icons.php,
generated from the shipped CSS + SVG fonts), a zibsvg group parsed from
the runtime sprite so it cannot drift, and GET /aksrt/v1/icons/catalog.
Shared admin pieces: aksrt_icon_markup()/aksrt_sanitize_icon_value()
with an SVG allowlist, the picker field/modal assets, and one canonical
aksrt-font-awesome handle registered through aksrt_enqueue_fontawesome().
kate522