Important
The native mobile app is no longer built/maintained, and instead now I only provide a link to an alternative here, which uses WebDav to sync the files/directories (the app already used that). This is simpler and probably safer, to be honest.
If you're looking for the last working version of the mobile app, it's at the v0.1.1 release or this commit.
If you're looking for the last failed attempt to upgrade it, check this PR.
I'm sorry, but there's not enough incentive for me to keep maintaining a native mobile app. I've heard great things about PhotoSync, though I haven't used it myself. Any WebDav client should work, and if it doesn't, feel free to open an issue at bewcloud/bewcloud.
