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/ui/ItemCount.tsx

@@ -14,7 +14,8 @@ const OVERFLOW_AT = 1_000_000;
 // "1M+", with the exact figure in the title tooltip. Deliberately generic ("item(s)", dynamic plural)
 // so any surface can reuse it for whatever it counts.
 export default function ItemCount({ count }: { count?: number }) {
-  const { t } = useTranslation();
+  const { t, i18n } = useTranslation();
+  const lang = i18n.language;
   // `count` is undefined only on a first, un-cached load — keep the fixed box (nothing shifts), just
   // show the icon until the number arrives.
   const label =
@@ -22,12 +23,12 @@ export default function ItemCount({ count }: { count?: number }) {
       ? ""
       : t("common.itemCount", {
           count,
-          formattedCount: count >= OVERFLOW_AT ? "1M+" : formatNumber(count),
+          formattedCount: count >= OVERFLOW_AT ? "1M+" : formatNumber(count, lang),
         });
   return (
     <span
       data-testid="item-count"
-      title={count == null ? undefined : formatNumber(count)}
+      title={count == null ? undefined : formatNumber(count, lang)}
       className="inline-flex h-7 min-w-[9rem] shrink-0 items-center justify-center gap-1.5 rounded-full bg-fg/8 px-3 text-sm whitespace-nowrap text-muted"
     >
       <Layers className="h-3.5 w-3.5 shrink-0 text-muted" aria-hidden="true" />