fix *arr rootfolders oneshot racing app startup

[jadeezomg]

Hey, ran into a problem where I changed my mounts and the service came up before the mounts did. Noticed ´mkWaitForApiScript´ already exists, just isn't used for the root folders.

Disclaimer: change was assisted by LLM. Full report/testing below

Report

<serviceName>-rootfolders is the only API reconciler that adds nixflix.serviceDependencies to its after/requires, so a remount of one of those mounts propagates a restart to it while <serviceName>.service is still coming back up. <serviceName>-config.service is RemainAfterExit=true and doesn't require those deps, so the wait-for-api it owns doesn't re-run — the reconciler's first curl -Sf $BASE_URL/rootfolder hits a closed port and set -e kills the oneshot with exit 7.

Hit on an NFS-backed host: sonarr-rootfolders started at 17:19:00 while sonarr.service only reached active at 17:19:02, with sonarr-config.service untouched since Jul 25. Fix reuses the ExecStartPre already on <serviceName>-config.service. Added VM test step fails on main with status=7/NOTRUNNING and passes with the fix.

Testing

Local nix build .#checks.x86_64-linux.<check> on x86_64-linux, flake.lock unchanged:
full-stack, sonarr-basic, radarr-basic, lidarr-basic, sonarr-anime-basic,
unit-tests, formatting — all pass.

With modules/arr-common/rootFolders.nix reverted to main and the new full-stack step
kept, the test fails with the reported signature:

[48.857626] sonarr-rootfolders.service: Main process exited, code=exited, status=7/NOTRUNNING
!!! RequestedAssertionFailed: command `systemctl restart --no-block sonarr.service;
    systemctl restart sonarr-rootfolders.service` failed (exit code 1)

With the fix, all four *arr services reconcile after a restart racing app startup:

sonarr root folders reconciled after a restart racing app startup!
sonarr-anime root folders reconciled after a restart racing app startup!
radarr root folders reconciled after a restart racing app startup!
lidarr root folders reconciled after a restart racing app startup!

Not run locally: jellyfin/prowlarr/seerr/maintainerr/qbittorrent/sabnzbd/recyclarr basics,
the caddy/nginx/postgresql/vpn integration tests, docs-build — none instantiate
rootFolders.nix.

[kiriwalawren]

Good catch! Thank you so much for the PR!

[jadeezomg]

thank you for this sweet flake!