feat(scripts): add csvdt, CSV timestamp normalisation

[YardQuit]

In support of teamdfir/sift#684, opened at Rob Lee's request that csvdt be added to the SIFT Workstation project.

Adds csvdt, a command-line CSV parser whose subject is timestamps: it reads epoch, ISO 8601 and Windows FILETIME in a column and writes any of them back, localised to a named zone. The use it is meant for on SIFT is bringing a timeline assembled from several parsers onto one clock before the rows are correlated.

Disclosure: I am the author of csvdt. Happy to change any of the below, and equally happy to close this if it turns out not to be something SIFT wants to carry.

• Installed as the upstream musl-static binary, from a pinned immutable release tag with an explicit SHA256, to /usr/local/bin/csvdt. The rolling release tag is deliberately not used: its artefacts are rebuilt monthly against a newer IANA tzdata, so its checksum moves and a pin to it would fail source_hash on every install after the next rebuild.
• Guarded to amd64 — upstream publishes no Linux arm64 binary yet. I would rather add aarch64-unknown-linux-musl upstream and drop the guard than have SIFT carry an arch gap on my account; say the word and I will do that before this is merged.
• Renovate annotation included: one GitHub-hosted asset with a single digest, which is the case the custom manager in .github/renovate.json handles. Checked against that regex as renovate applies it (dotAll, whole file) — it captures currentValue and currentDigest together, so a bump arrives as a matching pair rather than a new version against a stale hash.
• The manual page is rendered by the binary itself at install time (--generate-man), from the same definitions that parse its options, so the page on the image cannot describe an option the installed build lacks. mandb is tolerated as absent.
• Registered in sift/scripts/init.sls in both the include: list and the test.nop require: list.

Applied in the saltstack-tester image on 22.04/3007 and 24.04/3006: three states, none failed, and a second run reports all three Clean. The installed binary reports csvdt 1.0.0+2026.08.8609888 (IANA tzdata 2025b) and writes a 68 KB man page. man -w does not resolve it inside the tester image, but only because that image is a minimized Ubuntu with man-db removed — which is the case the (mandb -q || true) tolerance is there for.

License: GPL-3.0-or-later. Source: https://github.com/YardQuit/csvdt