fix(firms): label a snapshot that ends at a set time with that time, not LIVE

A FIRMS source may answer the 24 hours to a set time, naming its end as
`at` (epoch ms). The layer row then reads "24 h to MM-DD HH:MM UTC"
instead of "LIVE · updated ...", and getStats() reports `at`. A
snapshot without `at` (the trailing 24 hours to now, as the dev proxy
serves) keeps the LIVE label. Translated in every catalog.

src/layers/firms/queries.js

@@ -8,7 +8,7 @@ import {
   rampTrackGradient,
   sliderPositionForFrp,
 } from '../../data/firmsIntensity.js';
-import { formatNumber, t } from '../../i18n/index.js';
+import { formatNumber, formatUtcDayMonth, t } from '../../i18n/index.js';
 import { LOD_LEVELS, REFRESH_INTERVAL_MS } from './policy.js';
 
 /** Slider resolution: whole-percent positions along the log axis. */
@@ -190,8 +190,9 @@ export function createQueries({
      * Layer stats for the data panel. Degraded feed states surface through
      * `error` (established qa-failstate pattern: a dead feed must never look
      * like a healthy empty layer) with a matching human `loadingLabel`:
-     * 'LIVE · updated Xm ago' fresh, 'STALE · cached Xh' when the proxy
-     * served past-TTL cache, 'KEY REQUIRED' keyless.
+     * 'LIVE · updated Xm ago' fresh, '24 h to MM-DD HH:MM UTC' for a
+     * snapshot that ends at a set time (`at`), 'STALE · cached Xh' when the
+     * proxy served past-TTL cache, 'KEY REQUIRED' keyless.
      */
     getStats() {
       const now = Date.now();
@@ -213,6 +214,11 @@ export function createQueries({
         loadingLabel = staleText;
       } else if (layerState._error) {
         loadingLabel = layerState._error;
+      } else if (Number.isFinite(layerState._at)) {
+        loadingLabel = t('24 h to {day} {time} UTC', {
+          day: formatUtcDayMonth(layerState._at),
+          time: new Date(layerState._at).toISOString().slice(11, 16),
+        });
       } else if (layerState._lastUpdate) {
         loadingLabel = t('LIVE · updated {age}', {
           age: components.model.formatAgoMinutes(now - layerState._lastUpdate),
@@ -226,6 +232,9 @@ export function createQueries({
         lastUpdate: layerState._lastUpdate,
         loading: layerState._loading,
         stale: layerState._stale,
+        // The end of the 24 hours shown when the snapshot ends at a set time;
+        // null for the trailing 24 hours to now.
+        at: Number.isFinite(layerState._at) ? layerState._at : null,
         // The machine-readable half of the keyless state, ahead of the human
         // strings below: without it "no key configured" is indistinguishable
         // from a broken feed, and the row reads as a fault instead of a step