Add ability to validate photos on phone, compared to server and then re-queue files that are missing

[aaronnad]

Currently if a Photo or Video fails to upload using the auto-upload feature, then a quick red-bar message is displayed but you are not given the option to retry the upload, nor does it store the video/photo in a queue to be retried at a later date.

This means that some Photos and Videos are being missed on auto-upload and unless extreme close attention is paid, some content may be missed.

It would be nice if either in the same settings location as the auto-upload feature, a user can click a button to perform a manual recheck of all photos in their camera roll, then compare that to the NextCloud instance and validate whether the files are present.

Those that are then not present, are re-added to the queue automatically (or can be a radio button as part of the re-check to queue these automatically) so that content can be uploaded.