fix: numbers follow the UI language, not the browser's

`n.toLocaleString()` groups in the BROWSER's locale, so an English UI in a
Hungarian browser printed "1 234 567" while a Hungarian UI in an English
browser printed "1,234,567" — the number half of the date defect fixed in
618ef812. One `formatNumber` in lib/format.ts (a per-language cached
Intl.NumberFormat, like the relative-time formatters beside it) now serves
every grouped figure: Stats, Scheduler, the channel columns and the stats
popover, VideoCard's view tooltip, the ItemCount pill, and formatTotalHours.

ReleaseNotes' `toLocaleDateString(undefined, …)` was the one DATE site the
previous sweep missed; it moves onto formatDate.

The new cases assert both languages and that the two differ, instead of
comparing against the runtime's own default: that default is Hungarian on the
dev box and English on a CI image, so a one-language assertion would pass
under the old bug on half the machines. Verified in Chromium on :5173 with the
browser forced to hu-HU and the UI in English — Stats, Scheduler and the
channel table all keep comma grouping.

frontend/src/components/Scheduler.tsx

@@ -22,7 +22,7 @@ import { useLiveQuery } from "../lib/useLiveQuery";
 import { Button } from "./ui/Button";
 import { LoadingState, StateMessage } from "./ui/QueryState";
 import { useConfirm } from "./ConfirmProvider";
-import { relativeTime } from "../lib/format";
+import { formatNumber, relativeTime } from "../lib/format";
 import { notify } from "../lib/notifications";
 import Tooltip from "./ui/Tooltip";
 import { notifyActionError } from "../lib/actionErrors";
@@ -103,9 +103,9 @@ function JobProgress({ p }: { p: SchedulerJob["progress"] }) {
         <span className="truncate">{phase}</span>
         <span className="tabular-nums shrink-0">
           {p?.total != null
-            ? `${p.current.toLocaleString()} / ${p.total.toLocaleString()}`
+            ? `${formatNumber(p.current)} / ${formatNumber(p.total)}`
             : p
-              ? p.current.toLocaleString()
+              ? formatNumber(p.current)
               : ""}
         </span>
       </div>
@@ -291,7 +291,7 @@ function MaintenanceSettings({
       </div>
       <div className="text-2xs text-muted mt-1.5">
         {t("scheduler.maintenance.batchNote", {
-          default: m.revalidate_batch_default.toLocaleString(),
+          default: formatNumber(m.revalidate_batch_default),
         })}
       </div>
     </div>
@@ -540,31 +540,31 @@ export default function Scheduler() {
             icon={Database}
             label={t("scheduler.queue.recentPending")}
             hint={t("scheduler.queue.recentPendingHint")}
-            value={data.queue.channels_recent_pending.toLocaleString()}
+            value={formatNumber(data.queue.channels_recent_pending)}
           />
           <Stat
             icon={Database}
             label={t("scheduler.queue.deepPending")}
             hint={t("scheduler.queue.deepPendingHint")}
-            value={data.queue.channels_deep_pending.toLocaleString()}
+            value={formatNumber(data.queue.channels_deep_pending)}
           />
           <Stat
             icon={Clock}
             label={t("scheduler.queue.enrichPending")}
             hint={t("scheduler.queue.enrichPendingHint")}
-            value={data.queue.videos_pending_enrich.toLocaleString()}
+            value={formatNumber(data.queue.videos_pending_enrich)}
           />
           <Stat
             icon={Clock}
             label={t("scheduler.queue.shortsPending")}
             hint={t("scheduler.queue.shortsPendingHint")}
-            value={data.queue.videos_pending_shorts.toLocaleString()}
+            value={formatNumber(data.queue.videos_pending_shorts)}
           />
           <Stat
             icon={RadioTower}
             label={t("scheduler.queue.liveRefresh")}
             hint={t("scheduler.queue.liveRefreshHint")}
-            value={data.queue.videos_live_refresh.toLocaleString()}
+            value={formatNumber(data.queue.videos_live_refresh)}
           />
         </div>
       </div>
@@ -579,15 +579,15 @@ export default function Scheduler() {
             <Gauge className="w-4 h-4 text-muted shrink-0" />
             <span>
               {t("scheduler.quotaUsed", {
-                used: data.quota.used_today.toLocaleString(),
-                budget: data.quota.daily_budget.toLocaleString(),
+                used: formatNumber(data.quota.used_today),
+                budget: formatNumber(data.quota.daily_budget),
               })}
             </span>
             <span className="flex-1" />
             <span className="text-muted text-xs">
               {t("scheduler.quotaRemaining", {
                 count: data.quota.remaining_today,
-                formatted: data.quota.remaining_today.toLocaleString(),
+                formatted: formatNumber(data.quota.remaining_today),
               })}
             </span>
           </div>