delete should take a record id, not a file name: it's silly to go to the trouble of reading exif data & generating a new image record, just to get the id of an existing record so we can delete it.

And since purge.js is getting the to-be-deleted list from the database, it already has record ids....
Replace purge.py (which examined the file system to find images to delete) with purge.js (which relies on the database - specifically, the keep_until field - to decide where the great axe shall fall).

Mildly dissatisfied with using fs.unlinkSync() to do the file removal. Seems like there ought to be a promise-y way of chaining that together with the db record deletion. Must RTFM.