fix the docker image

Looks like the docker image is a bit broken, there are few things I need to investigate:

• Why can't the bot see libraries that are installed (sympy, pint)
• Why does the bot flat out ignore the bot admins commands (probably a typo/error in the compose)
• Can the bot be ported to matrix-native (that way it can use native multiline support)
• Can we publish to our registery rather than / as well as dockerhub - as docker hub now has pull limits and nukes images after 2 years
• Can we use postgres as the DB backend (rather than sqlite/flat files) so it's easier to persist data between rebuilds (and I can back it up easier :)).