Pass the Dag bundle's team to secrets backends during Dag parsing

[taehwoi]

Secrets backends receive team_name during task execution, but during Dag file parsing it was always None, so team-scoped connections and variables did not resolve in top-level Dag code (see #65530).

What changes:

• The Dag processor manager gives each parsing process an in-process API client whose requests carry the bundle name (airflow-dag-bundle-name header).
• InProcessExecutionAPI reads that header into a new TIClaims.bundle_name claim. get_team_name_dep resolves the team from DagBundleModel when the claim is set, and from the task instance otherwise, so variables and connections routes need no changes.
• Only the in-process app reads the header. The API server takes identity from the signed token and ignores it, so a worker cannot use it to reach another team's secrets.
• Parse-time variable writes and key listing become team-scoped as well, matching task execution.

Design note, feedback welcome: the in-process app is shared by every parsing process in the manager, so the bundle identity has to travel with each request. A header read only by the in-process auth override was the smallest carrier I found. Alternatives considered: a query parameter honored by the real server (spoofable from a task token), resolving secrets directly in the manager (bypasses the execution API), a signed token minted by the Dag processor (needs the JWT key there). If another carrier fits the AIP-92 direction better, I am glad to switch.

Not included: the triggerer has the same gap (TriggerRunnerSupervisor.team_name is known but not passed); it can reuse this mechanism through its make_client seam in a follow-up.

closes: #70495

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

• Yes - Claude Code (Claude Fable 5)

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

[boring-cyborg]

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