Incorrect initialization of end time for a new task

[lredor]

Creating a task within a work package that has both a start date and an end date does not behave correctly.

The start date of the task is correct, aside from the time zone issue described in #26.
However, the end date should reuse the work package’s end date with a time set to 23:59, not 00:00.

Steps to reproduce:

• Create a work package with a start date of 10/04/2026 and an end date of 16/04/2026.
• Create a task within this work package.
• Expected:
  • The start date of the new task is 10/04/2026 00:00.
  • The end date of the new task is 16/04/2026 23:59