Mobile DevOps: Code signing with project-level secure files

What this post added

Introduced Project-level Secure Files as a new feature in GitLab 15.0, allowing users to upload and store sensitive binary files (e.g., keystores, signing certificates, provisioning profiles) directly within a GitLab project but outside of version control. Detailed the process of uploading these files via the UI and demonstrated how to download them within a CI/CD job using the `glab CLI` tool, enabling their use in mobile code signing workflows.