Problem with assigning a core UI

For example, Assigned cores disappear from the UI. This is problematic for obvious reasons. But sometimes users may want to assign cores to tasks that are NOT theirs, yet is the ability to manipulate cores (splitting) after assignment possible? Or can a user "unassign" a core assigned to task?

There are also ways we can improve the UI on this page to show the time better rather than RegionIDs which are opaque to the user. We should AT LEAST have block numbers, but preferrably do things always based on date and time, ideally grabbing the user's timezone from their browser.

Also, the cores are sorted arbitrarily. We need proper groupings, AND in-group sorting that makes sense, not necessarily customizable by the user.

Note
Once you take on this PR paste a comment with your hand -> ✋ so that people know that someone is working on this issue.

Start by reviewing the core assignment UI described in the issue and reproduce how assigned cores disappear. Clarify whether reassignment, splitting, and unassignment are required, then define the desired date/time, grouping, and sorting behavior. Done means the assignment state remains understandable and the UI presents meaningful, consistently grouped core information.