Fix remove file on initial comment (go-gitea#20127)

- Backport go-gitea#20127
  - Store the file uuid(which is returned by Gitea in the upload file response) onto the file object, so it can be used for the remove feature to specify this file.
  - Resolves go-gitea#20115

Author: Gusted

Diff for: web_src/js/features/common-global.js

@@ -192,7 +192,8 @@ export function initGlobalDropzone() {
       thumbnailWidth: 480,
       thumbnailHeight: 480,
       init() {
-        this.on('success', (_file, data) => {
+        this.on('success', (file, data) => {
+          file.uuid = data.uuid;
           const input = $(`<input id="${data.uuid}" name="files" type="hidden">`).val(data.uuid);
           $dropzone.find('.files').append(input);
         });