Allow users to enter 0 hours for instant reassignment

[mau11]

Fixes # (issue)

Description

Issue

• dynamic assignments do not support a 0 hour response window
• when 0 is entered in the input, the value disappears:
  https://github.com/user-attachments/assets/f90a7a37-59f3-4659-847d-d980a866ea21

This branch fixes the UX and adds support for a 0 hour response window

Checklist:

• I have manually tested my changes on desktop and mobile
• The test suite passes locally with my changes
• If my change is a UI change, I have attached a screenshot to the description section of this pull request
• My change is 300 lines of code or less, or has a documented reason in the description why it’s longer
• I have made any necessary changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• My PR is labeled [WIP] if it is in progress

[mau11]

future - we need to add a linter to the repo to avoid these type of indentation updates