OpenVapeCN/VapeService ? reverse-engineered prompt

Build me a local only Java service for testing an old Vape 4.21 style client, with one app that serves both the legacy Online REST endpoints and the Zeus TCP connection.

It should keep all data in a local JSON file instead of using a database, and it needs to start with sensible defaults for localhost. Include the login and browser confirmation flow, basic account creation when a username does not exist, profile and settings read and write, friends and friend requests, online status, private messages, parties with invites and kicking and transferring ownership, plus the Minecraft profile and server sync pieces. Also handle activity updates, world changes, inventory and hand slot snapshots, CPS forwarding, heartbeats, display names, health checks, and a few admin style queries.

Make it runnable from the command line with bind address, HTTP port, Zeus port, and data file options, and keep it safe for local testing only. If you need to check any current Java or networking details, look them up online first.