Simplify restic and healthchecks reporting

[josephst]

Can the service configuration be simplified to no longer require a large mess of systemd files and shell scripts for reporting start/stop/success and output?

Goals:

• split up systemd units into smaller components - one for backup, one for checking, one for maintenance & pruning
• avoid having to write plaintext uuid to files (is there a way for Agenix to manage?)