feat(design): the Copy rule — names, verbs, dates and units (E28 S3g)

The owner's picks (all the recommended options) become DESIGN.md's Copy
chapter and a sweep of both languages (742 values, no key drift):

- One name per feature: the rail's label, which may shorten it (Alerts
  -> Notifications, Fiókok -> Felhasználók, Download Center -> Downloads,
  Channel manager -> Channels); one "sync from YouTube" verb.
- Four verbs, four meanings (Delete / Remove / Dismiss / Discard, and
  their Hungarian pairs), checked against what each action does.
- Sentence case, the app's places capitalised; "…" on a command that
  asks first (a popover or form title got its own key without it);
  one-sentence messages without a stop or a tick, "Couldn't …"; curly
  quotes.
- Dates only from lib/format.ts, in the UI language: formatDateTime
  names the month and stops at the minute (it printed "9/27/2026,
  8:30:14 AM"), formatDateTimeSec for the log, the audit and the
  recorder; ui/RelativeTime pairs "3d ago" with the exact minute on
  hover. local/date-format refuses toLocale*String and Intl date
  formatters elsewhere.
- Units from Intl, short (formatUnit): runtimes, totals, the Scheduler
  countdown, the stats range, the player's tap skip. "2h 13m" was
  English in both languages.
- src/i18n/copyRule.test.ts holds the machine-readable part (quotes,
  "...", ticks, bare unit letters).

frontend/src/components/IssueComposer.tsx

@@ -5,7 +5,7 @@ import { ExternalLink, FileText, Plus, Server, X } from "lucide-react";
 
 import { api, type DebugScreenshot, type DebugSession, type ServerLogRow } from "../lib/api";
 import { closeComposer } from "../lib/debugRecorder";
-import { formatBytes } from "../lib/format";
+import { formatBytes, formatDateTimeSec, formatUnit } from "../lib/format";
 import { notify } from "../lib/notifications";
 import { useMe } from "../lib/useMe";
 import {
@@ -303,8 +303,8 @@ function ComposerBody({
     <div ref={root} className="flex flex-col gap-4">
       <p className="text-sm text-muted">
         {t("recorder.composer.meta", {
-          start: started.toLocaleString(i18n.language),
-          minutes,
+          start: formatDateTimeSec(started.toISOString()),
+          minutes: formatUnit(minutes, "minute"),
           level: t(`settings.diagnostics.levels.${session.level}`),
         })}
       </p>