florium: forum on libhttppp/libhtmlpp/libdbpp (mammut), fenrirds and mediadb

BB code via libvbulletinpp (submodule), categories/forums/threads with
quoting, editing, moderation, search; fenrirds accounts, groups and group
policies (global + per forum), e-mail verified registration (libsmtppp),
user control centre, avatars in fenrirds (FFmpeg -> WebP), images and logo
in mediadb, favicon from the logo, themes incl. FenrirOS with light/dark,
multiple domains (DOMAINS), setup wizard and administration on its own
HTTPS port, supervisor restart, Docker image on FenrirOS.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>