Create PAT with workflow scope for Dependabot auto-merge

[LarsEckart]

Problem

Dependabot PRs that modify workflow files (like .github/workflows/test.yml) cannot be auto-merged using the default GITHUB_TOKEN. GitHub requires a token with the workflow scope.

Example: PR #411 (actions/cache bump) failed auto-merge with:

GraphQL: Pull request refusing to allow a Personal Access Token to create or update workflow 
`.github/workflows/test.yml` without `workflow` scope (enablePullRequestAutoMerge)

Solution

1. Create a new Personal Access Token (classic) with repo and workflow scopes
2. Add it as a repository secret (e.g., AUTO_MERGE_TOKEN)
3. Update the auto-merge step in .github/workflows/test.yml to use this token instead of GITHUB_TOKEN

Security consideration

Be aware that using a PAT gives more permissions than the default token. Consider if manual merging of workflow-modifying PRs is acceptable instead.