Package as deb for easier upgrades

[runleveldev]

Currently, the application is only packaged as a docker image. This makes updates difficult on non-docker deployments as the full software needs built for that server on each update, the exact process for which varies between updates. We should instead build the main components (agent, manager, docs) as .deb packages hosted via GitHub releases which can be installed to handle updating all relevant files and restarting relevant services.

[runleveldev]

The docker images should build and install the deb files for consistency.

[runleveldev]

The hard part is DB migrations. I'd like the server process to apply migrations at startup with a lock on the database.