fix(calendar): localize cron start_time to timetable timezone before computing planned runs

[waterWang]

Closes #71234

Problem

Calendar view's planned/future runs for cron-based timetables are computed
in UTC wall-clock instead of the DAG's configured timezone. When a DAG
uses a non-UTC default_timezone (e.g. Asia/Seoul, UTC+9) with a cron
schedule like "0 8 * * *", the planned runs appear at 17:00 instead of
08:00 — exactly a UTC-vs-local offset.

The root cause is in CalendarService._calculate_cron_planned_runs():
croniter receives last_data_interval.end (a UTC-aware datetime) as
start_time and reads its timezone — UTC — so the cron expression is
matched against UTC wall-clock. The real scheduler (CronMixin._get_next)
correctly localizes the start time to the timetable's own timezone before
calling croniter.

Fix

1. Add imports for convert_to_utc, make_aware, make_naive from
   airflow._shared.timezones.timezone (same utilities used by
   CronMixin._get_next).

2. In _calculate_cron_planned_runs:

   • Extract the timetable's _timezone from the CronMixin cast.
   • Localize start_time to that timezone via make_naive() before
     constructing croniter.
   • Convert each result back to UTC via convert_to_utc(make_aware(...)).

This matches the exact pattern used by CronMixin._get_next() in
airflow/timetables/_cron.py.

Testing

All 19 existing calendar tests continue to pass. The fix was verified
locally by the issue reporter with an additional regression test for a
non-UTC cron timetable (20/20 passing).

Related

• Calendar view computes planned runs for cron timetables in UTC, ignoring the DAG's configured timezone #71234 (original issue report with full reproduction steps)
• Calendar view does not respect user-selected timezone #67477 (fixed frontend layer; this completes the fix at the backend)
• Fix airflow dags clear clearing the wrong day for non-UTC partitioned timetables #67717 (same pattern, fixed in airflow dags clear)
• Support partitioned Dags in calendar view #63631 (added timezone-aware next_dagrun_info_v2 path for non-cron timetables)

[kaxil]

Closing this as part of a cleanup of a large batch of PRs opened in quick succession from this account.

18 PRs have been opened here in the past two weeks and none have merged. Several show signs of being generated and submitted without review: #71432 and #71433 are the same change across the same five files, opened two minutes apart, and several titles carry a leaked agent identifier that other contributors already flagged as garbled text on #70629 and #71322.

Airflow is maintained by volunteers. Every PR costs reviewer time and CI capacity, so a high volume of unvetted submissions has a real cost to the project.

You are welcome to keep contributing. Please open one change at a time, run it locally against the tests, and read the contributors' guide before submitting. If you think a specific change here is correct, comment with the reasoning and a maintainer can reopen it.