CLI: Download and import media from a URL

[lastzero]

As a user who often imports videos or other media from the Web, I want an import command that takes a URL as an argument so I don't have to manually download the file first.

This should save an extra step for users who want to archive online videos that are available on social media sites or as M3U8 streaming URLs, e.g.:

photoprism dl https://youtu.be/fD6VYfy3B2s

[lastzero]

The changes above add a "photoprism dl [url]" command that allows you to download and import videos directly from a URL.

An updated development preview build will be available soon so you can test it without building from source:

• https://docs.photoprism.app/release-notes/#development-preview