Rename PSGallery API key secret from `APIKEY` to `PSGALLERY_API_KEY`

[MariusStorhaug]

Context and Request

The PSGallery publish secret is currently named APIKEY across the PSModule organization. This name is ambiguous — it gives no indication of what system the key belongs to.

Renaming it to PSGALLERY_API_KEY makes the secret self-describing, consistent with common naming conventions for organization secrets, and easier to audit.

Acceptance criteria

• The organization secret is renamed from APIKEY to PSGALLERY_API_KEY.
• The Process-PSModule workflow references PSGALLERY_API_KEY instead of APIKEY.
• Any documentation referencing the old name is updated.
• Publishing to PSGallery continues to work after the rename.

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Technical Decisions

Rename approach — Remove the old secret and create the new one with the same value, or rename in-place if the GitHub UI/API supports it. The old name must not remain active once the new name is in use to avoid confusion.

Rollout order — Update the secret in the organization first, then update the workflow reference in the same PR to avoid a window where the workflow references a non-existent secret.

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Implementation Plan

• Rename or recreate the organization secret from APIKEY to PSGALLERY_API_KEY in the PSModule GitHub organization settings.
• Update the Process-PSModule workflow (publish step or equivalent) to reference secrets.PSGALLERY_API_KEY instead of secrets.APIKEY.
• Search for any other workflow files in the organization that reference APIKEY and update them.
• Update any documentation that references the APIKEY secret name.
• Verify a publish run succeeds after the change.