plugins/container/v0.7.2

fix(ci): take bullseye-security from the snapshot mirror

Debian 11 reached end of life on August 31st, 2026, and the Debian archive
started removing the bullseye-security binaries while the index still lists
them. Every build in the debian:bullseye container now fails in the very
first apt step with 404 errors (gpgconf, libpython3.9-minimal, libperl5.32,
...), on both architectures, including the release workflow.

Dropping the bullseye-security source is not enough: the image already ships
the security versions of libc6, perl-base and gpgv, and the plain bullseye
suite cannot satisfy their dependencies.

Use the snapshot.debian.org mirror the image itself was built from (the image
ships the URL as a commented line in /etc/apt/sources.list) and accept its
expired Release file. Apply the same change to the container plugin CI, which
runs in the same image.

Signed-off-by: Leonardo Grasso <me@leonardograsso.com>