Add “State” filter (open/closed/all) to project board alongside label filter

[WldFalcon]

Feature Description

Currently, project boards in Gitea allow filtering cards by labels and assignees (introduced in #31999), but there is no quick way to filter by issue/PR state.
When a project contains a large number of closed issues or merged PRs, they can clutter the board and make it harder to focus on active work.

Proposed solution:
Add a “State” filter dropdown to the project board filter bar (next to the existing label and assignee filters) with three options:

• Open — show only open issues and open PRs
  

• All — show all issues and PRs (default, current behavior)
  

• Closed — show only closed issues and closed/merged PRs
  

  The filter should work the same way as the label filter via query string
  Should be applied across all columns of the board.
  “Closed” should include closed issues and closed/merged PRs.

Screenshots

No response