Allow to archive labels (#26478)

## Archived labels 

This adds the structure to allow for archived labels.
Archived labels are, just like closed milestones or projects, a medium to hide information without deleting it.
It is especially useful if there are outdated labels that should no longer be used without deleting the label entirely.

## Changes

1. UI and API have been equipped with the support to mark a label as archived
2. The time when a label has been archived will be stored in the DB

## Outsourced for the future

There's no special handling for archived labels at the moment.
This will be done in the future.

## Screenshots

![image](https://github.com/go-gitea/gitea/assets/80308335/208f95cd-42e4-4ed7-9a1f-cd2050a645d4)

![image](https://github.com/go-gitea/gitea/assets/80308335/746428e0-40bb-45b3-b992-85602feb371d)

Part of https://github.com/go-gitea/gitea/issues/25237

---------

Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/features/comp/LabelEdit.js

@@ -36,7 +36,7 @@ export function initCompLabelEdit(selector) {
     $('.new-label.modal').modal({
       onApprove() {
         $('.new-label.form').trigger('submit');
-      }
+      },
     }).modal('show');
     return false;
   });
@@ -49,6 +49,9 @@ export function initCompLabelEdit(selector) {
     const nameInput = $('.edit-label .label-name-input');
     nameInput.val($(this).data('title'));
 
+    const isArchivedCheckbox = $('.edit-label .label-is-archived-input');
+    isArchivedCheckbox.prop('checked', this.hasAttribute('data-is-archived'));
+
     const exclusiveCheckbox = $('.edit-label .label-exclusive-input');
     exclusiveCheckbox.prop('checked', this.hasAttribute('data-exclusive'));
     // Warn when label was previously not exclusive and used in issues
@@ -64,7 +67,7 @@ export function initCompLabelEdit(selector) {
     $('.edit-label.modal').modal({
       onApprove() {
         $('.edit-label.form').trigger('submit');
-      }
+      },
     }).modal('show');
     return false;
   });