Fix task state store custom expiry datetime missing timezone on save

[amoghrajesh]

---

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closes: #68747

What

Saving a task state store entry with a custom expiry date fails with a 422. The datetime-local input returns a bare YYYY-MM-DDTHH:mm string, but the API requires a timezone-aware datetime.

Error was:

{
    "detail": [
        {
            "type": "timezone_aware",
            "loc": [
                "body",
                "expires_at",
                "datetime"
            ],
            "msg": "Input should have timezone info",
            "input": "2026-07-22T10:25"
        },
        {
            "type": "literal_error",
            "loc": [
                "body",
                "expires_at",
                "literal['default']"
            ],
            "msg": "Input should be 'default'",
            "input": "2026-07-22T10:25",
            "ctx": {
                "expected": "'default'"
            }
        }
    ]
}

Current behaviour

Editing an existing entry auto-selects "Custom" expiry (the API always returns a resolved absolute datetime). Clicking Save sends "2026-07-22T10:25" and the API rejects it with Input should have timezone info.

Proposed change

Convert the picker value to a timezone-aware ISO string via dayjs.tz(customExpiresAt, selectedTimezone).toISOString() before sending. Extracted into a getExpiresAt() helper to replace the nested ternary in onSave. Applies to both add and edit flows.

Same flow works fine now:

curl 'http://localhost:28080/api/v2/dags/example_task_state_store/dagRuns/manual__2026-06-22T05%3A13%3A57.081200%2B00%3A00/taskInstances/run_job/state-store/abcd?map_index=-1' \
  -X 'PUT' \
  -H 'Accept: application/json' \
  -H 'Accept-Language: en-GB,en;q=0.9' \
  -H 'Connection: keep-alive' \
  -H 'Content-Type: application/json' \
  --data-raw '{"expires_at":"2026-07-22T05:14:00.000Z","value":1000}'

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[guan404ming]

LGTM

[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.

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Status	Branch	Result
✅	v3-3-test