As drily as I can, given the rules of Show HN, but it's not end-to-end if the crypto is delivered over browser Javascript. Every time a user's browser touches your server for any reason, the server has the option to fatally compromise security. End-to-end means you don't have to trust the server; that's real privacy.
So, given that this is a proof-of-concept, my advice is to back off on the web app part of this, and develop an installable client.
So, given that this is a proof-of-concept, my advice is to back off on the web app part of this, and develop an installable client.