StopWebServer() only stopped a RUNNING server, while ShutdownWebServer()
joined in any state but STOPPED. Shutting down while the server was
still STARTING joined a thread nobody had told to stop, which then
entered its loop and never left. Stop it while STARTING too, and only
switch to RUNNING if no stop came in meanwhile.
Also make the report.ppsspp.org registration cancellable. It runs at
startup and every nine minutes, and couldn't be interrupted, so exiting
during a stalled one waited out its connect and 900s header timeouts.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
