fix: address remaining widget review feedback

apps/docs/docs/widgets/timetable/index.mdx

@@ -34,3 +34,5 @@ import streetDepartures from "./img/street-departures.png";
 ### Configuration
 
 <WidgetConfig configuration={timetableWidget.configuration} />
+
+For security, new or changed custom base URLs must resolve to a public IP address. Private and local hosts are rejected.

apps/docs/docs/widgets/timetable/index.ts

@@ -11,7 +11,7 @@ export const timetableWidget: WidgetDefinition = {
       {
         name: "Search.ch URL",
         description: "Base URL for the Search.ch timetable API.",
-        values: "Any valid URL.",
+        values: "An HTTP(S) URL that resolves to a public IP address.",
         defaultValue: "https://search.ch",
       },
       {