caddy v2.11.4-3 -- restore v2.11.4-2's GC'd promoted image at a new version

The v2.11.4-2 registry manifest (sha256:14cc7a0b5a5fd04efa17396576c83cc6d59690d988008f3f68ff90b50c55d95b)
was garbage-collected before its 14 pins in dunn.dev/iac were ever
merged against a live manifest. This repo's registry retention policy
has since been fixed to prevent recurrence.

Rebuilding v2.11.4-2's exact tag was considered and rejected: this
commit's three FROM bases (registry.gitlab.com/dunn.dev/pipeline/ci-go,
ci-runtime-go, and docker.io/busybox) are all floating tags, not
digest-pinned, and docker.io/busybox:1.37.0-musl was independently
confirmed to have been repushed (2026-07-31) after the original
2026-07-01 build. A rebuild under the old tag would carry genuinely
different content -- different busybox bytes, and no committed go.sum
to lock the Go module graph either -- while claiming to be the same
version. v2.11.4-3 is the honest label for that new content; source
is otherwise identical (same Caddy v2.11.4, cloudflare v0.2.4,
ratelimit v0.1.0 module pins; same Containerfile).