Drop Python 3.10 and fix scan exceptions after the version update

[csandanov]

Builds for Python 3.10–3.13 have failed the vulnerability scan since the version update on 2026-10-02, so revision r3 was never published. The scan exceptions were pinned to the previous Python versions and stopped matching once the versions changed.

This change makes the builds pass again:

• Python 3.10 is dropped. It reaches end of life this month and still fails the scan on two High findings. Published 3.10 tags stay available.
• Python 3.11.17 gets one exception for CVE-2026-82049. This version already contains the upstream fix; the vulnerability data just does not list a fixed 3.11 release yet. Removal is tracked in Remove CVE-2026-82049 exception for Python 3.11.17 once the scanner records the fix #21.
• Stale exceptions are removed. 3.12.15 and 3.13.16 pass the scan without one.

Details

• .grype.yaml: a single rule, CVE-2026-82049 for the python binary at exactly 3.11.17.
• Removed PYTHON310 from the workflow matrix, the revision alias map, the base image pins, and the README tag list.

Validation

• The pull request build runs the full matrix including the scan.

Follow-up

• Tag a new image revision after merging; r3 points at a commit that cannot pass the scan.

Closes #10
Closes #12