feat: add application deadline for status: applying

status:
- default to applied.
- when the user chooses applying tag, there is another box that posts 'application deadline'.
- any other tags do not have the application deadline, as any past 'applying' stage do not need it.

Look at the code handling job application statuses and tags, likely in a models or services directory. Find where the 'applying' tag is processed and add a field for 'application deadline'. Update the UI forms to conditionally show this input. Test by creating an application with the 'applying' tag and verifying the deadline is saved and displayed.

Written by the indexing model from the issue text.