Add "Regenerate thumbnail" action to document UI[Feature Request]

Description it would be useful to have a "Regenerate thumbnail" action directly in the document UI. Currently, thumbnails can be regenerated using the management command: document_thumbnails --document <id> This requires shell access to the Paperless-ngx installation. A menu action such as "Regenerate thumbnail" or "Refresh thumbnail" in the document's action menu would make this much more convenient. A typical use case is a PDF that was initially password protected. After removing the password in Paperless-ngx, the document can be opened normally, but the existing thumbnail may still be the generic document icon. The thumbnail can be regenerated via the command line, but there is no corresponding action in the web UI. Other useful cases would include: regenerating a thumbnail after modifying or replacing a document version recovering from a failed thumbnail generation refreshing a stale or missing thumbnail Ideally, …