feat(native): the app needs TREK 5.1.3 on the server and checks a remembered one once after the update

The fixes that keep the app's sign-in in the app live in the server's UI,
so an updated app on a 5.1.2 server still ended in the browser. The server now
reports nativeApi 2 and the app refuses anything below it, naming 5.1.3.

A server the app remembers from before is not loaded unchecked: the first
launch after the update shows the address screen filled in with it, says why
and checks it right away. A server that is new enough loads again with its
session; an older one gets the update hint.

server/src/nest/health/features.controller.ts

@@ -69,7 +69,10 @@ export class FeaturesController {
       // The version of what the apps rely on from the server (the hand-off
       // routes, the shell bridge in the served UI). Raised only for a change an
       // older app cannot follow; the app refuses a server below its minimum.
-      nativeApi: 1,
+      // 2 (5.1.3): the browser sign-in starts under /api, past an older TREK's
+      // service worker, and the hand-off page signs in by itself. Apps from then
+      // on refuse a server below it, so its users stop landing in the browser.
+      nativeApi: 2,
       // The other way round: the oldest app binary this server's UI works with,
       // as the shell API the app reports (TrekShell.getCapabilities). An app
       // below it is asked to update instead of running native calls it lacks.