Show each Dag only once in airflow dags list

[Eason09053360]

Airflow 3 stores one serialized_dag row per Dag version, but airflow dags list
selected every row without filtering by version, so a Dag was printed once per
version it had.

Use the existing SerializedDagModel.read_all_dags() helper, which selects the
row with the highest version_number per dag_id.

Note that #60868 / #61077 fixed one source of spurious version growth, but
legitimate versions still accumulate whenever a Dag is edited, so the duplicate
rows remain reproducible.

closes: #60594

This supersedes #60637, which reached the same diagnosis but was closed by the
stale bot without review.

---

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

• Yes — Claude Code (Opus 5)

Generated-by: Claude Code (Opus 5) following the guidelines

---

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[henry3260]

Well done!

While reviewing this I noticed DBDagBag.iter_all_latest_version_dags()
(airflow-core/src/airflow/models/dagbag.py) has the same issue — the name says
latest-version, but the body is an unfiltered select(SerializedDagModel). Same
origin as this one (#53918 dropped the read_all_dags() call in both places).
Out of scope here. would you mind fixing it in a follow-up PR?

[github-actions]

Hi maintainer, this PR was merged without a milestone set.
We've automatically set the milestone to Airflow 3.3.2 based on: backport label targeting v3-3-test
If this milestone is not correct, please update it to the appropriate milestone.

This comment was generated by Milestone Tag Assistant.

[github-actions]

Backport successfully created: v3-3-test

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
✅	v3-3-test

[Eason09053360]

@henry3260 Thanks for reviewing !
Sure I will take a look on it and push a follow up pr :)