[feature]: Sub-issue collapse state in list view not persisted across page refreshes

Summary:
When collapsing/hiding sub-issues under their parent in the list view, the collapse state is not persisted. Every time the page is refreshed, all sub-issues are expanded again, forcing the user to manually collapse them again.

Steps to reproduce:

1. Open a project with parent issues that have sub-issues
2. Collapse/hide sub-issues under a parent in the list view
3. Refresh the page
4. All sub-issues are expanded again

Expected behavior:
The collapse state should be persisted (e.g., in local storage, user preferences API, or as part of the view settings) so that refreshing the page or navigating away and back preserves which parents have their sub-issues collapsed.

Why this should be worked on:
Projects with many nested issues become tedious to navigate when every refresh resets the view. This is basic UX polish that significantly impacts daily workflow for users managing deeply nested work items.

Start at the list-view implementation and trace how parent issue collapse state is currently held during refreshes. Review any existing view-settings or persistence tests, then verify that collapsing selected parents remains preserved after a page refresh and after navigating away and back.