Add project column picker to issue and pull request sidebar (#37037)

Why? You are working on a ticket, it's ready to be moved to the QA
column in your project. Currently you have to go to the project, find
the issue card, then move it. With this change you can move the issue's
column on the issue page.

When an issue or pull request belongs to a project board, a dropdown
appears in the sidebar to move it between columns without opening the
board view. Read-only users see the current column name instead.

* Fix #13520
* Replace #30617

This was written using Claude Code and Opus. 

Closed:

<img width="1346" height="507" alt="image"
src="https://github.com/user-attachments/assets/7c1ea7ee-b71c-40af-bb14-aeb1d2beff73"
/>

Open:
<img width="1315" height="577" alt="image"
src="https://github.com/user-attachments/assets/4d64b065-44c2-42c7-8d20-84b5caea589a"
/>

---------

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: Cursor <cursor@cursor.com>

models/issues/issue_project.go

@@ -115,17 +115,10 @@ func IssueAssignOrRemoveProject(ctx context.Context, issue *Issue, doer *user_mo
 			panic("newColumnID must not be zero") // shouldn't happen
 		}
 
-		res := struct {
-			MaxSorting int64
-			IssueCount int64
-		}{}
-		if _, err := db.GetEngine(ctx).Select("max(sorting) as max_sorting, count(*) as issue_count").Table("project_issue").
-			Where("project_id=?", newProjectID).
-			And("project_board_id=?", newColumnID).
-			Get(&res); err != nil {
+		newSorting, err := project_model.GetColumnIssueNextSorting(ctx, newProjectID, newColumnID)
+		if err != nil {
 			return err
 		}
-		newSorting := util.Iif(res.IssueCount > 0, res.MaxSorting+1, 0)
 		return db.Insert(ctx, &project_model.ProjectIssue{
 			IssueID:         issue.ID,
 			ProjectID:       newProjectID,