Enable gateway-based data recovery path

[cdata]

We've encountered at least one case where the local block storage becomes corrupted and is apparently unrecoverable: https://github.com/subconsciousnetwork/subconscious/issues/693

A blunt solution that will likely "fix" this for the majority of users is to delete the whole database and re-initialize it, and subsequently synchronize it with a configured gateway. This does depend on a user having sync'd to a live gateway somewhat recently, but otherwise the only caveat is that they will lose most of the locally cached data that pertains to other spheres than their own.