Pin templ version in docker-deps (fixes Docker CI build)

[joestump]

The docker-deps Make target installed templ@latest, which as of v0.3.1020 requires Go >= 1.25 — but the Dockerfile builder image is golang:1.24 with GOTOOLCHAIN=local, so every Build and Push CI job has failed since 2026-05-22 (first failing run: https://github.com/joestump/spotter/actions/runs/26277286030).

ci-deps already pins templ to the version in go.mod; this applies the identical pattern to docker-deps, making the Docker build reproducible and consistent with the tested module version.

Found while working the Spotter remediation board (https://github.com/users/joestump/projects/98) — this pre-existing failure was masking Docker-build signal on every remediation PR.

🤖 Posted on behalf of @joestump by Claude.

[joestump]

Independent review — LGTM ✅

Verified:

• Diff scope: Makefile only (2 lines). Pins templ in docker-deps and also in the local deps target — both copy the exact pattern already used by ci-deps (go install github.com/a-h/templ/cmd/templ@$(shell go list -m -f '{{.Version}}' github.com/a-h/templ)), so all three targets now install the same templ version.
• Diagnosis confirmed: Dockerfile builder is FROM golang:1.24 and go.mod pins github.com/a-h/templ v0.3.977 (predates the Go ≥ 1.25 requirement introduced in v0.3.1020), so @latest was the only thing incompatible with the builder image.
• Proof it works: the Build and Push check ran the actual docker build (Buildx "Build and push Docker image" step) on this PR's head and passed (https://github.com/joestump/spotter/actions/runs/29073514298/job/86300830692), alongside passing Lint and Test.
• No regressions expected: $(shell go list -m ...) only reads go.mod (works before go mod download), and local dev via make deps now gets the go.mod-tested templ version instead of a drifting @latest — a strict improvement for reproducibility.

One note: this pins to whatever go.mod says, so future templ upgrades happen via go get bumps — which is exactly the desired behavior.

🤖 Posted on behalf of @joestump by Claude.