Change GID of app group when changing UID of app user

[zonescape]

Currently changing UID of the app user makes the app group orphaned. Also app user becomes a member of an unknown group:

# docker container run -it --rm --env APP_UID=1000 umputun/baseimage:app-v1.14.0 sh
init container
set timezone America/Chicago (Tue Dec  3 04:30:02 CST 2024)
set custom APP_UID=1000
execute sh

/ $ id
uid=1000(app) gid=1000 groups=999(docker),1000
/ $ groups
1000groups: unknown ID 1000
 docker

and we have strange file ownership in /home/app:

/ $ touch /home/app/test
/ $ ls -l /home/app/test
-rw-r--r--    1 app      app              0 Dec  3 04:36 /home/app/test
/ $ ls -n /home/app/test
-rw-r--r--    1 1000     1001             0 Dec  3 04:36 /home/app/test

[umputun]

LGTM, thx.

@paskal you fine with this change?