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/RelativeTime.dom.test.tsx

@@ -4,6 +4,7 @@
 import { afterEach, describe, expect, it } from "vitest";
 import { cleanup, render } from "@testing-library/react";
 import { formatDateTime, formatDateTimeSec, relativeTime } from "../../lib/format";
+import "../../i18n"; // the real instance, in English: the component names time in the UI language
 import { RelativeTime } from "./RelativeTime";
 
 afterEach(cleanup);
@@ -14,8 +15,8 @@ describe("RelativeTime", () => {
   it("says how long ago, and names the exact minute on hover", () => {
     const { container } = render(<RelativeTime at={THREE_DAYS_AGO} />);
     const el = container.querySelector("time")!;
-    expect(el.textContent).toBe(relativeTime(THREE_DAYS_AGO));
-    expect(el.getAttribute("title")).toBe(formatDateTime(THREE_DAYS_AGO));
+    expect(el.textContent).toBe(relativeTime(THREE_DAYS_AGO, "en"));
+    expect(el.getAttribute("title")).toBe(formatDateTime(THREE_DAYS_AGO, "en"));
     expect(el.getAttribute("dateTime")).toBe(THREE_DAYS_AGO);
   });
 
@@ -23,7 +24,7 @@ describe("RelativeTime", () => {
     const ms = Date.parse(THREE_DAYS_AGO);
     const { container } = render(<RelativeTime at={ms} seconds />);
     expect(container.querySelector("time")!.getAttribute("title")).toBe(
-      formatDateTimeSec(THREE_DAYS_AGO),
+      formatDateTimeSec(THREE_DAYS_AGO, "en"),
     );
   });