Potential fix for code scanning alert no. 7: Workflow does not contain permissions

[perinst]

Potential fix for https://github.com/perinst/dozu-api-service/security/code-scanning/7

To fix the issue, we will add a permissions block to the workflow. This block will be added at the root level to apply to all jobs unless overridden by job-specific permissions blocks. Based on the workflow's operations, the minimal required permissions are:

• contents: read for accessing repository contents (e.g., during the build job).
• No write permissions are required since the workflow does not modify repository contents or perform actions like creating releases.

We will add the following permissions block at the root level:

permissions:
  contents: read

This ensures that the GITHUB_TOKEN has only read access to repository contents, adhering to the principle of least privilege.

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