On Windows with Hyper-V/WSL2/Docker, port 8080 is often reserved by the
OS (EACCES) or already in use (EADDRINUSE), making sign-in completely
impossible. The app now scans 8080–8089 and binds the first available
port. For DCR providers, a stale registration locked to a blocked port
is detected and cleared so the client re-registers on the new port.
Static-client providers (Google BYOK) keep fixed-port behaviour with a
clear error message instead of a raw Node.js exception.
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