Switch official Docker images to Debian Trixie

[ytoprakc]

Update Airflow’s Docker image base from Debian Bookworm to Debian Trixie.

Airflow’s documented base OS policy says the project switches released images to the latest supported Debian stable version approximately six months before the previous stable version reaches the end of regular support. Debian Bookworm regular support ended on July 11, 2026, so the Docker image base should now move forward to Debian Trixie.

This PR updates the Docker image build defaults, Breeze image build defaults, CI workflow inputs, and Docker stack documentation/examples from Bookworm to Trixie. It also records the change in the Docker image changelog and adds a significant newsfragment because this is user-visible for anyone pulling, extending, or rebuilding Airflow images.

closes: #71494

What changed:

• Updated production and CI image defaults to use debian:trixie-slim.
• Restricted supported Debian image builds in Breeze to trixie.
• Updated image build workflows to default to trixie.
• Updated Docker stack docs, examples, and build references from Bookworm to Trixie.
• Updated Debian installation/security docs to describe Trixie as the reference Debian platform.
• Added Docker image changelog and release-note coverage for the base image migration.
• Added a Breeze regression test to assert the Debian image default remains Trixie.

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Was generative AI tooling used to co-author this PR?

• Yes — OpenAI Codex

Generated-by: OpenAI Codex following the guidelines

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• Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
• For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
• When adding dependency, check compliance with the ASF 3rd Party License Policy.
• For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.