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/plexPlayerControls.tsx

@@ -3,6 +3,7 @@ import { useTranslation } from "react-i18next";
 import { RotateCcw } from "lucide-react";
 import { IconButton } from "./ui/IconButton";
 import { Slider as Range, CheckRow } from "./ui/NativeControls";
+import { formatDecimal, formatUnit } from "../lib/format";
 
 // --- settings-panel building blocks ------------------------------------------------------------
 export function PanelHead({ children }: { children: ReactNode }) {
@@ -17,6 +18,7 @@ export function Slider({
   max,
   step,
   suffix,
+  seconds,
   onChange,
   onReset,
 }: {
@@ -25,20 +27,24 @@ export function Slider({
   min: number;
   max: number;
   step: number;
+  /** A symbol after the number ("%", "px"). */
   suffix?: string;
+  /** The value is seconds: named in the UI language's unit ("0.5 sec" / "0,5 mp"). */
+  seconds?: boolean;
   onChange: (v: number) => void;
   onReset?: () => void;
 }) {
-  const { t } = useTranslation();
+  const { t, i18n } = useTranslation();
+  const lang = i18n.language;
+  const shown = seconds
+    ? formatUnit(value, "second", lang)
+    : `${formatDecimal(value, lang, 1, 0)}${suffix ?? ""}`;
   return (
     <div className="px-1 py-1">
       <div className="mb-1 flex items-center justify-between text-[0.75rem] text-white/80">
         <span>{label}</span>
         <span className="flex items-center gap-1.5">
-          <span className="tabular-nums text-white/60">
-            {Number.isInteger(value) ? value : value.toFixed(1)}
-            {suffix ?? ""}
-          </span>
+          <span className="tabular-nums text-white/60">{shown}</span>
           {onReset && (
             <IconButton
               variant="overlay"