bug: Enable Dependabot security updates

[fantonangeli]

Describe the Bug

The repository currently has several open security alerts, including high-severity vulnerabilities.
The current Dependabot configuration only groups regular version updates.

Steps to reproduce

1. Open the repository Dependabot alerts.
2. Notice multiple old unresolved security alerts.

Expected Behavior

Dependabot security updates should be enabled and grouped into a dedicated security update PR.

Editor Version

No response

Platform

Web / Browser

Additional Context

No response