docs: record verified Android login fix artifact and regression results

docs/login-troubleshooting.md

@@ -16,6 +16,11 @@ AndroidKeyStore encryption and absolute expiry remain unchanged. The native clie
 does not depend on weakening the server or changing its configuration. For browser
 security, server operators should still use `SESSION_SECURE=true` on HTTPS sites.
 
+[Download the fixed 0.2.1 preview APK ZIP](https://git.nesterovic.cc/nessi/Yuvomi-App/actions/runs/666/artifacts/android-native-debug-apk)
+(verified Gitea build job 1071; repository access required, 14-day retention).
+Extract `app-debug.apk` and install it. The downloaded artifact's version and
+signature were checked and installation/launch tested on the authorized emulator.
+
 ## Error distinctions
 
 - Rejected username/password: the server rejected `/auth/login` with HTTP 401.