[A11y] Label the API keys table actions column

[cursor]

Problem

The API keys table actions column uses an empty <th />. The team table labels similar headers.

Proposed change

Add aria-label="Actions" (or visible “Actions”) on that header.

Why this matters

Screen reader users otherwise hear an unlabeled column in the keys table.

Suggested implementation

• apps/dashboard/app/dashboard/settings/keys/ApiKeysClient.tsx

Acceptance criteria

• Actions column has an accessible header
• Tests added/updated where applicable
• Documentation updated where applicable

Contributor notes

This should be a good first contribution and does not require deep knowledge of the Telemetry Tracker architecture.

Open PRs against develop. See CONTRIBUTING.md.