scaleway/compute-instance v4.0.0

By pigeon.dev wiki

A census of every scaleway/compute-instance consumer (live and historical, via git log -S) found exactly one real caller, and it was already working around the module's own redundancy: it hardcoded profile = "pigeon-cli" (profile = "docker" has never been instantiated anywhere), and re-declared the same bucket secret three separate times across buckets, keyring_entries, and environment_variables just to keep their aliases in sync by hand.

This PR:

Drops the docker profile and the profile variable entirely — pigeon-cli provisioning (rclone/neovim, the bootstrap script, keyring/rclone config, Cockpit/Alloy) is now the module's only, unconditional behavior.
Renames namespace/name to name_prefix/name_suffix.
Groups SSH access under a new user_config object; ssh_keys (a list) becomes user_config.ssh_key (a single string) — the only real caller ever passed one key.
Groups image (now optional, defaulting to "ubuntu_jammy"), type, and cockpit under a new instance_config object.
Collapses buckets + keyring_entries + environment_variables into one keyring list. A kind = "bucket" entry now also renders an rclone.conf remote; any entry's secret_key (never written into keyring.toml itself) now auto-exports PIGEON_SECRET_<ALIAS> on the instance, replacing the free-form environment_variables map.

Full rationale and the exact rendering changes: docs/adr/0118-simplify-scaleway-compute-instance-interface.md.

Breaking change — every top-level input except enable_ipv4/enable_ipv6/additional_volume_ids is renamed, regrouped, or removed. A follow-up PR migrates the one real consumer to the new interface and the new tag.

Test plan

mise run fmt-check-terraform passes.
tofu validate passes against the rewritten module in isolation.
After merge: confirm the v4.0.0 tag/GitHub Release and regenerated README Inputs/Outputs tables.

#157