feat(metadata): add original-language preferences (#526)

* feat(metadata): add original-language preferences

* fix(settings): show metadata exceptions immediately

* docs(settings): add metadata language screenshot

* fix(settings): make language exceptions responsive

* fix(settings): standardize language display names

web/src/lib/languageDisplay.ts

@@ -1,34 +1 @@
-// Catalog filter values for `original_language` are ISO 639-1 codes ("en",
-// "fr", "ja"). Surfaces show friendly names ("English", "French", "Japanese")
-// while keeping the underlying value untouched so query rules stay valid.
-
-let cachedDisplayNames: Intl.DisplayNames | null | undefined;
-
-function getDisplayNames(): Intl.DisplayNames | null {
-  if (cachedDisplayNames !== undefined) {
-    return cachedDisplayNames;
-  }
-  try {
-    cachedDisplayNames = new Intl.DisplayNames(["en"], { type: "language" });
-  } catch {
-    cachedDisplayNames = null;
-  }
-  return cachedDisplayNames;
-}
-
-export function formatLanguage(code: string): string {
-  const trimmed = code.trim();
-  if (!trimmed) return "";
-  const dn = getDisplayNames();
-  if (!dn) return trimmed.toUpperCase();
-  try {
-    const name = dn.of(trimmed);
-    if (name && name !== trimmed) {
-      // Intl.DisplayNames returns lowercase for some locales — capitalize.
-      return name.charAt(0).toUpperCase() + name.slice(1);
-    }
-  } catch {
-    // Fall through to fallback.
-  }
-  return trimmed.toUpperCase();
-}
+export { formatLanguage } from "@/lib/languageNames";