Add Azure Linux (AZL) source to production

[JamieMagee]

Overview

Add Azure Linux (AZL) as a source in the production instance of osv.dev. Microsoft publishes OSV-format advisories at microsoft/AzureLinuxVulnerabilityData, and the ecosystem already has full support in the codebase.

Closes #5041

Details

Adds an azurelinux entry to source.yaml. It's a Git-based source (type 0) that pulls AZL--prefixed JSON files from the osv directory of Microsoft's repo. The repo has around 12,000 advisories and is updated automatically a few times a day.

The equivalent entry was previously added to source_test.yaml and tested on the staging instance.

Testing

• Verified the import worked correctly on the test instance via source_test.yaml before promoting to production.
• Confirmed the repo structure, file prefix (AZL-), directory (osv), and extension (.json) match the upstream repo.
• Checked that the entry follows the same pattern as other Git-based sources like almalinux, bellsoft, and psf.