Round-trip test exposed it: during a rooted stint the WebUI (root-in-
container) writes root-owned files into its data dir; back in rootless the
WebUI user (dockerinstall) can't manage them -> container Exited(137).
Since the WebUI is LibrePortal's OWN regenerable 0:0 component, reconcile now
also chowns containers/libreportal to the mode's container owner (root rooted
/ install user rootless). Validated: after this the WebUI returns to HTTP 200.
Third-party app data under containers/ is still untouched (backup/restore).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Signed-off-by: librelad <librelad@digitalangels.vip>
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