feat(rail): add a Rail layer with keyless live trains

Live trains from 30 keyless operator feeds: GPS positions from 29 and
Irish Rail's station reports, shown as the operators publish them. 28
work out of the box; Renfe long and medium distance and KTMB appear once
their pack is built, because their vehicles name no route.

Packs are opt-in (scripts/build-rail-paths.mjs): the operator's own
route lines, stop names, next stops and trip-update delays for live
trains. Nothing downloads when the app starts, no train is placed from a
timetable, and no request carries a deployer's key.

src/i18n/locales/de.json

@@ -3452,6 +3452,21 @@
   "Play speed": "Wiedergabegeschwindigkeit",
   "Scroll or pinch to zoom, drag to move along · double-click to see it all": "Scrollen oder mit zwei Fingern zoomen, ziehen zum Verschieben · Doppelklick zeigt alles",
   "1 min/s": "1 Min./s",
+  "Rail": "Bahn",
+  "Urban rail": "Stadtverkehr",
+  "Local rail": "Nahverkehr",
+  "Regional rail": "Regionalverkehr",
+  "National rail": "Fernverkehr",
+  "International rail": "International",
+  "Hide {category}": "{category} ausblenden",
+  "Show {category}": "{category} einblenden",
+  "Live GPS": "Live-GPS",
+  "Estimated from station reports": "Geschätzt aus Bahnhofsmeldungen",
+  "To {headsign}": "Nach {headsign}",
+  "Next {stop} {time} {relative}": "Nächster Halt {stop} {time} {relative}",
+  "Prev {stop} {time} {relative}": "Letzter Halt {stop} {time} {relative}",
+  "(+{minutes} min late)": "(+{minutes} min Verspätung)",
+  "Exit cockpit to fly to a train": "Cockpit verlassen, um zu einem Zug zu fliegen",
   "Photo © {photographer}": "Foto © {photographer}",
   "The shared flight isn't reporting now — showing where it was last seen": "Der geteilte Flug sendet gerade nicht – letzte bekannte Position wird gezeigt",
   "The shared flight isn't reporting now — showing where it was at {time}": "Der geteilte Flug sendet gerade nicht – Position um {time} wird gezeigt",