fix: load docker-compose.override.yml in compose function

[ErnestHysa]

Fixes #2132 — compose() never loads docker-compose.override.yml.

This adds a check after the compose files are built to append the override file if it exists.

[agent932]

Tested this fix on a live umbrelOS install — confirms the behaviour described in #2132.

Applied the patch manually to /usr/local/lib/node_modules/umbreld/source/modules/apps/legacy-compat/app-script, placed a docker-compose.override.yml in the Plex app data directory with a custom volume mount (/mnt/UNAS-PlexStorage), and restarted. docker inspect confirmed the override was applied correctly.

Also validated update survivability: overwrote docker-compose.yml with the app store template (simulating an app update), restarted, and the override was still picked up cleanly. Apps without an override file were unaffected.

LGTM — clean, minimal, correct.

[DavidBurela]

I tried applying the patch locally as well.
Worked cleanly. The values in docker-compose.override.yml were correctly applied to the container.

[jjmmbb]

When will this be released? A very simple and extremly important change.

[agent932]

Hi @getumbrel, this PR addresses #2132 by enabling override compose files as documented. All tests pass and the change is minimal. Could you review when you have a chance? Thanks!

[agent932]

@lukechilds is there anything else I need to do for this PR?

[jjmmbb]

When will this fix be included in the UmbrelOS update?