v1.50.65 – v1.50.66 — 2026-08-03

• feat(release): align APT channel model with enconf (suite/component pattern)
• feat(release): stable/testing APT channel system for mailguard/debian registry
• fix(installer): handle testing→stable channel downgrade with --allow-downgrades
• release: v1.50.64 — bump version + release-doc
• release: v1.50.66 — bump version