www/tt-rss: Run ttrssd as ttrssd user and move data to /var

• Create a ttrssd user and group to run ttrssd.
• Move log file to /var/log/tt-rss directorie.
• Move pid files to /var/run/tt-rss directorie.
• Move on disk data to /var/tt-rss/.

PR: 282245
Approved by: maintainer
Differential Revision: https://reviews.freebsd.org/D49128