pkgs.phonetpm: 0.4.1 -> 0.4.2

Branches, PRs and auto-merge now use the UPDATE_PKGS_TOKEN repo secret
instead of GITHUB_TOKEN, so the normal pull_request ci.yml run (with the
farm build) shows up on each PR and GitHub merges it with a merge commit
once the ruleset is met. The serial verify job (rebase, dispatch ci.yml,
wait, merge) and the final ci dispatch on master are gone: the auto-merge
counts as the token's, so the push to master triggers ci.yml itself.

UPDATE_PKGS_TOKEN: fine-grained PAT (or GitHub App token) for this repo
with Contents: read/write, Pull requests: read/write and Workflows:
read/write (force-pushing an update branch rebased over master commits that
touched .github/workflows is refused without it). The repo needs "Allow
auto-merge" enabled. The workflow fails early if the secret is missing.

Grafana 13 no longer ships the prometheus datasource as a core plugin, so the provisioned VictoriaMetrics datasource was unusable. Switch it and the dashboards to victoriametrics-metrics-datasource.

Every NixOS machine runs Vector (host metrics, internal metrics, journal)
and writes to VictoriaMetrics/VictoriaLogs on both styx and coaxmetal,
each sink with a 512 MiB disk buffer. Both servers run vmalert (metrics and
LogsQL instances), a two-node Alertmanager cluster posting to Matrix via
matrix-alertmanager-receiver, Gatus (results scraped into VictoriaMetrics,
alerted on by vmalert) and Grafana with provisioned datasources and
dashboards. All ports are open on retiolum only.

Replaces telegraf on neoprism, including the borgbackup status file.