Investigate options for replacing 1 year secrets for GitHub Actions

**Is your feature request related to a problem? Please describe.**
Enterprise app secrets expire after 1 year, GitHub doesn't know when this is going to expire and so Actions just stop working when the secret expires.

We should investigate to see if there are any better alternatives to using Enterprise App Secrets.

**Describe the solution you'd like**
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**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
Add any other context or screenshots about the feature request here.

No files, workflows, tests, or concrete alternatives are named. Start by reviewing the repository's GitHub Actions configuration and Azure Enterprise App Secret usage, then document a viable replacement and how secret expiry or rotation would be handled; done means the team has a decided, actionable alternative.

Written by the indexing model from the issue text.