V1GoneController

Answers every /api/v1 path with 410 Gone and a pointer to v2.

Callers are unmigrated v1 clients, so the body keeps the v1 error shape ({error, message}) that they already parse.

Deliberately does not extend BaseController, whose constructor connects to the database unconditionally: /api/v1 is public, so that is a connection per request for a response that reads nothing.