Previously, the insights collector would only try to get an admin user once
at startup. If no admin user existed (e.g., fresh database before first user
registration), insights collection would silently fail forever.
This change moves the admin context creation inside the collection loop so it
retries on each interval. It also updates log messages in WithAdminUser to
remove the Scanner prefix since this function is now used by other components.
Signed-off-by: Deluan <deluan@navidrome.org>
e36fef8692