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/lib/collate.ts

@@ -0,0 +1,13 @@
+// Alphabetical order in the UI language (E30 S3): Hungarian puts "Ö" after "O" and "Cs" after "Cu". A
+// bare `localeCompare` compares in the BROWSER's locale; the server sorts by the same ICU rules
+// (backend `app/collation.py`), so a list sorted here agrees with one the server sorted. Its own
+// module, apart from lib/format.ts, because it needs no i18n: the pure sort helpers import it.
+const collators = new Map<string, Intl.Collator>();
+export function compareText(a: string, b: string, lang: string): number {
+  let c = collators.get(lang);
+  if (!c) {
+    c = new Intl.Collator(lang);
+    collators.set(lang, c);
+  }
+  return c.compare(a, b);
+}