feat: establish automated and manual accessibility gates

src/presentation/components/async-surface.jsx

@@ -1,7 +1,12 @@
 /** @param {{ label?: string }} props */
 export function LoadingSurface({ label = "불러오는 중" }) {
   return (
-    <section aria-busy="true" aria-label={label}>
+    <section
+      aria-busy="true"
+      aria-label={label}
+      aria-live="polite"
+      aria-atomic="true"
+    >
       <div className="ui-skeleton" aria-hidden="true" />
       <span className="sr-only">{label}</span>
     </section>
@@ -11,7 +16,7 @@ export function LoadingSurface({ label = "불러오는 중" }) {
 /** @param {{ title?: string, action?: React.ReactNode }} props */
 export function EmptySurface({ title = "표시할 항목이 없습니다.", action }) {
   return (
-    <section className="ui-empty">
+    <section className="ui-empty" aria-live="polite">
       <p>{title}</p>
       {action}
     </section>