Let the News panel narrow the window to 12, 6, 3 or 1 hours

The panel's window label becomes a choice of the server's window and each
shorter one. The feed and map filter to it locally; the hotspot counts are
read again for it (/api/news/hotspots?hours=N, now on the allowlist). A
server names the longest window it serves as maxWindowHours.

changelog.d/1-news-layer.md

@@ -1,6 +1,7 @@
 - Add the News layer (Events ▸ News) and its right-rail NEWS panel: the last
-  24 hours from curated hotspots (or the fewer hours a server names, shown in
-  the panel), coloured by severity only, with hotspot
+  24 hours from curated hotspots (or the fewer hours a server names), narrowed
+  in the panel to the last 12, 6, 3 or 1 hours with the hotspot counts read for
+  that window, coloured by severity only, with hotspot
   beacons, outlines with disputed areas, picture cards for major events, an
   "In view" list below 3,000 km and a continuous feed whose cards fly the globe
   to the event. Core serves no news itself: set `GEV_NEWS_ORIGIN` to a news