Fix custom timetable generate_run_id not called for manual triggers

[NilsJPWerner]

In Airflow 3.x, commit 035060d (PR #46616) changed the trigger_dag module to use DagRun.generate_run_id() instead of
dag.timetable.generate_run_id() for manual DAG runs. This bypassed custom timetable logic, causing a regression from Airflow 2.x behavior.

This commit restores the use of dag.timetable.generate_run_id() for manual triggers, allowing custom timetables to control run_id generation for both scheduled and manually triggered runs.

Changes:

• airflow/api/common/trigger_dag.py: Changed to call dag.timetable.generate_run_id() with run_after and data_interval parameters instead of DagRun.generate_run_id()
• tests/api_fastapi/core_api/routes/public/test_dag_run.py: Added test to verify custom timetable generate_run_id is called for manual triggers with both logical_date provided and null

This pattern matches how manual triggers are handled in other parts of the codebase (e.g., assets.py, scheduler_job_runner.py).

Fixes: #55908

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[NilsJPWerner]

cc @sunank200 @uranusjr

[NilsJPWerner]

A little bump on this. Would love to get this in for 3.1.1 @kaxil

[pierrejeambrun]

LGTM but I'll wait for another pair of eyes.

[pierrejeambrun]

CI need fixing.

[NilsJPWerner]

CI need fixing.

They seem unrelated to my changes. I rebased but it didn't seem to retrigger ci

[pierrejeambrun]

I just rebased the PR, lets see if the CI is happy now.

[pierrejeambrun]

static check need fixing, this is related to your code change.

[NilsJPWerner]

static check need fixing, this is related to your code change.

Sorry I misread the position of the ruff check. I have fixed it now.

[uranusjr]

Need to fix test, otherwise this makes sense to me.

[NilsJPWerner]

When fixing the tests I realized I also needed to fix this in the fastapi endpoint.

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[github-actions]

Backport successfully created: v3-1-test

Status	Branch	Result
✅	v3-1-test