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.

src/i18n/locales/de.json

@@ -72,6 +72,7 @@
   "Reading the news…": "Nachrichten werden gelesen…",
   "News, last {hours} hours": "Nachrichten der letzten {hours} Stunden",
   "Last {hours} h": "Letzte {hours} Std.",
+  "Time window": "Zeitraum",
   "Hotspots": "Brennpunkte",
   "Severity": "Schweregrad",
   "Category": "Kategorie",