v0.37

• Add pgBackRest v2.59.0 #73:
  • Build pgBackRest 2.59.0 from upstream distribution tarballs. Assign label latest to v2.59.0.
  • Delete info about pgBackRest v2.55.0.
  • Keep older Meson and GPDB builds on source archive Dockerfiles.
• Add AGENTS.md and update LICENSE for 2026 #74.
• Bump alpine, ci and e2e version #75:
  • Switch to alpine 3.23 in Dockerfile.alpine.
  • Bump github action versions.
  • Update e2e tests:
    • Update MinIO image to RELEASE.2025-09-07T16-13-09Z.
    • Update MinIO MC image to RELEASE.2025-08-13T08-35-41Z.
    • Update Nginx image to 1.30.4-alpine.
    • Bump PG to 18.

Full Changelog: v0.36...v0.37