LinuxServer.io containers must start as root to perform user setup via
the PUID/PGID mechanism. Setting runAsUser/runAsGroup in the container
securityContext breaks the s6-overlay init system, causing permission
errors when trying to modify /etc/passwd and /etc/group.

Changes:
- Remove runAsUser and runAsGroup from securityContext
- Keep podSecurityContext.fsGroup for volume permissions
- Add documentation explaining LinuxServer.io container requirements
- Bump chart version to 0.1.1

Fixes deployment errors:
- usermod: cannot lock /etc/passwd
- groupmod: Permission denied
- s6-rc: unable to start service init-adduser