Migrate to official Renovate GitHub App and remove self-hosted workflow

[harryswift01]

Summary

This PR removes the self-hosted Renovate GitHub Actions workflow and transitions the repository to use the official Renovate GitHub App instead. This simplifies maintenance, improves scalability across the CCPBioSim organisation, and ensures PRs are authored by renovate[bot].

Changes

Remove self-hosted Renovate GitHub Action

• Deleted .github/workflows/renovate.yml
• Removed dependency on a personal or machine-user PAT
• Prevents duplicate Renovate runs between the Action and the App

Clean up Renovate-related secrets

• Removed the RENOVATE_TOKEN secret as it is no longer required
• Eliminated PAT rotation/maintenance for Renovate

Update renovate.json to improve scheduling and PR clarity

• Added a weekday morning schedule (before 8am on weekdays)
• Added automatic "dependencies" label to all Renovate PRs
• Retained all existing best-practices presets and rules

Impact

• Renovate PRs will now be authored by the official renovate[bot]
• No more GitHub Actions minutes consumed for Renovate
• Reduced maintenance burden (no PATs, no workflow updates)
• More scalable approach for managing Renovate across CCPBioSim repos
• Cleaner and more consistent dependency update workflow

[jimboid]

This looks correct based on the documentation for "hosted by somebody else" with a github app installed on the org. Config on the org checks out ok. Please merge.

[jimboid]

You might be able to reduce the scope of dependabot or eliminate it entirely.

[harryswift01]

You might be able to reduce the scope of dependabot or eliminate it entirely.

Yeah this is very true, I will let this run a few times so we can see how it can handle everything but yeah this can very much repalce dependabot so we have just one dependency updater and make it easier to understand and avoid duplication. We can also confgure this very easily now with other repos on the CCPBioSim organisation which is very handy.