fix(i18n): numbers, units, dates and order in the UI language, and after a switch (E30 S3)

Every locale formatter takes the language as an argument. Under the React
Compiler a formatter that read the i18n singleton was memoized on its other
arguments, so a card kept "2 hr 4 min" after a switch to Hungarian; plexLang()
had the same flaw and left Plex queries in the old language. Components now
take the language from useTranslation, and the signature makes forgetting it
a type error.

- ratings, file sizes, stream stats: the language's decimal mark ("8,3")
- view and subscriber counts compact in the language ("1,2 E")
- seconds as the language's unit ("6 mp") in the sliders and the stats
- a person's birth and death dates as dates, not ISO strings
- A-Z lists by the shown name in the language's alphabet (compareText),
  the tag catalog re-sorted by its translated names
- lint local/locale-format (was date-format) also refuses Intl.NumberFormat
  outside lib/format.ts, localeCompare, and a component reading the language
  off the i18n singleton

frontend/src/components/About.tsx

@@ -8,10 +8,10 @@ import { formatDateTime } from "../lib/format";
 import { Button } from "./ui/Button";
 import Modal from "./ui/Modal";
 
-function fmtDate(d?: string | null): string {
+function fmtDate(d: string | null | undefined, lang: string): string {
   if (!d) return "—";
   const t = new Date(d);
-  return isNaN(t.getTime()) ? d : formatDateTime(d);
+  return isNaN(t.getTime()) ? d : formatDateTime(d, lang);
 }
 
 // About dialog: app + build + schema versions (frontend/backend/database), plus a
@@ -23,7 +23,8 @@ export default function About({
   onClose: () => void;
   onOpenReleaseNotes: () => void;
 }) {
-  const { t } = useTranslation();
+  const { t, i18n } = useTranslation();
+  const lang = i18n.language;
   const { data } = useQuery({
     queryKey: qk.version(),
     queryFn: api.version,
@@ -40,7 +41,7 @@ export default function About({
       data ? data.app_version + (data.git_sha !== "unknown" ? ` · ${data.git_sha}` : "") : "…",
     ],
     [t("about.database"), data?.db_revision ?? "…"],
-    [t("about.buildDate"), fmtDate(data?.build_date ?? FRONTEND_BUILD_DATE)],
+    [t("about.buildDate"), fmtDate(data?.build_date ?? FRONTEND_BUILD_DATE, lang)],
   ];
 
   return (