scaleway/compute-instance v5.3.1

This moves the ADR-0109/0110/0114 short module-source redirect mechanism (noisypigeon.com/modules/<provider>/<module>/vX.Y.Z and noisypigeon.com/templates/zola-site/vX.Y.Z) off the personal-blog domain and onto pigeon.dev, which already runs the identical Zola/zola-site hosting pipeline (ADR-0130) with zero new Terraform resources needed.

generate-module-redirects.sh, its two templates (module-redirect.html, theme-redirect.html), and its two generated-content directories (content/modules/, content/theme-versions/) move from workloads/noisypigeon.com/src/ to workloads/pigeon.dev/src/. .mise.toml's pigeon-dev-build/pigeon-dev-serve tasks, pigeon-dev-pages.yml, noisypigeon-com-deploy.yml, and template-release.yml's post-tag deploy dispatch are rewired accordingly. The public URL path convention (modules/<provider>/<module>/vX.Y.Z) stays exactly as ADR-0110 fixed it — only the hostname changes, and every short URL still resolves to the identical git::...?ref=... target it did before.

This PR also updates compute-instance's own internal composition (iam.tf, instance.tf, which source iam-policy/iam-api-key/ block-volume via the short URL) and every templates/terraform/ module README's usage example from noisypigeon.com to pigeon.dev. Because compute-instance already has prior tags, this PR's edit to its tracked .tf content will trigger a real (if purely cosmetic) v5.3.1 patch release via the existing changed-module release automation — see ADR-0136 for why that's accepted rather than avoided.

This is PR A of a two-PR cutover (see ADR-0136's "Decision" section). A second PR will sweep every workloads/*/terraform/** consumer leaf's source = line from noisypigeon.com to pigeon.dev, opened only once this PR has merged and pigeon-dev-pages.yml has deployed the new redirect pages live.

New ADR: docs/adr/0136-move-module-redirect-urls-to-pigeon-dev.md.

#223