MedEvac: email notification scheduler UI

[morgang-adappt]

Description

Adds the Schedule Alert step to the email notification wizard: a cron editor bound to { scheduleEnabled, cronValue }, behind a single applyCronValidity() gate. Enabling a schedule with no saved value seeds a valid default (0/5 * 1/1 * *), the invalid-cron snackbar is debounced, and Next stays disabled while the schedule is enabled and the cron is invalid - including when editing a notification whose saved cron is legacy or invalid.

Also adds a minutes unit to the "in the last" filter, which scheduled notifications need for sub-hourly polling windows. This touches the shared convert-to-minutes helper and the filter row; the existing minutes base is kept, so there is no change for other consumers.

Useful links

• MedEvac: email notification scheduler ems-backend#1261
• Function PR

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.

• Test A
• Test B

Screenshots

Checklist:

( * == Mandatory )

• * I have set myself as assignee of the pull request
• * My code follows the style guidelines of this project
• * Linting does not generate new warnings
• * I have performed a self-review of my own code
• * I have put the ticket for review, adding the oort-frontend team to the list of reviewers
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• * I have put JSDoc comment in all required places
• * My changes generate no new warnings
• * I have included screenshots describing my changes if relevant
• * I have selected labels in the Pull Request, according to the changes with code brings
• I have made corresponding changes to the documentation ( if required )
• I have added tests that prove my fix is effective or that my feature works
• * New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[GhaziAlibi]

everything works as expected