relative paths and redirects

[bertsky]

Fixes:

• the Dozzle (logview) needs a redirect to the respective (configured) port on the same host as the request
• the workspace log path must be relative to the overall /data volume, too
• the overall /data volume must be used as base path
• the current state of the ocrd_browser requires building from the repository (see Dockerfile: use local pkg, not PyPI hnesk/browse-ocrd#56)