Add additional time picker for time(and date) based fields in TaskDialog

[its-me-abhishek]

Is your feature request related to a problem? Please describe.
we already support adding dates while creating a task in taskwarrior, but the current ui does not allow users to explicitly select time for time-based fields. this makes it inconvenient or unclear when users want precise scheduling (for example, a due date at a specific hour rather than just a day).

Describe the solution you'd like
add additional date + time pickers in TaskDialog for taskwarrior time-based fields.
the supported fields should be:

• due
• start
• end
• entry
• wait

Expected ui / ux flow

1. user clicks on a time-based field (e.g., due) to edit that or just add a new one in case it does not exist
2. first, prompt the user to select a date
3. once a date is selected, prompt the user to select a time
4. combine both and store/send the final value in a taskwarrior-compatible datetime format
5. ensure the value works seamlessly with the existing backend

Important notes

• date-only selection should not silently assume time; time selection must be explicit ( in case the user adds one)
• formatting must strictly follow taskwarrior expectations
• add and update tests for this on backend/frontend for each field respectively
• should integrate cleanly with existing add-task flow without breaking current behavior

Checklist (fields to be covered)

• due
• start
• end
• entry
• wait

Additional context

Contribution notes

• this issue can be worked on via multiple prs
• the issue is intentionally unassigned
• please comment on the issue mentioning which field(s) you are working on, and we will keep an eye on it to avoid overlap

[its-me-abhishek]

https://time.rdsx.dev/
The AM/PM based Date&Time picker can be used to replace our existing DatePicker, and some backend/frontend tweaks would make this work. Can make use of this or some other implementation.