module: bump minimum Go version to 1.18 and use debug.ReadBuildInfo()

module: bump minimum Go version to 1.16

module: refactor Makefile, add help

miflorad: check meta data incl battery level every hour instead daily

- the battery voltage level seems to have more flexibility than one change a day
- short drops announcing end of battery life could go unnoticed

miflorad: shorten process termination timeout by listening for quit o…

…n every retry

module: adjust to less noisy schedule for digest dependencies and reb…

…ase stale PRs in renovate

module: ignore golang.org/x/net in renovate, align commit message