WebUI-driven commands (`setup finalize`, `backup`, restore) ran with an
empty $docker_install_user because cliInitialize only called
checkInstallTypeRequirement for the `app` category. The backup engine then
ran `sudo -E -u "" restic init`, which sudo rejects with a usage dump —
surfacing as "Failed to initialize Local disk" in the setup wizard.
Factor the user resolution out of checkInstallTypeRequirement into a
side-effect-free resolveDockerInstallUser (rooted -> sudo_user_name,
rootless -> CFG_DOCKER_INSTALL_USER, with fallbacks so it is never empty)
and call it at the cliInitialize chokepoint so all command categories get a
valid install user, not just app.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: librelad <librelad@digitalangels.vip>
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