Document Handshake Node

Add end-user documentation for Blink Labs Handshake Node.

## Scope

- Explain what the node provides and the supported networks.
- Cover installation and first-run guidance.
- Document configuration, peer connectivity, RPC, and persistent state.
- Include operational monitoring and troubleshooting.
- Describe CPU and Stratum mining support, clearly separating node operation from mining.
- Link to the source repository and release artifacts.

## Source

https://github.com/blinklabs-io/handshake-node

Start by reviewing the Handshake Node source repository and its release artifacts: https://github.com/blinklabs-io/handshake-node. Use the issue scope as the documentation checklist, covering supported networks, installation, first run, configuration, peers, RPC, persistent state, monitoring, troubleshooting, and the distinction between node operation and CPU or Stratum mining. Done means end users can follow the guidance and find the source and releases.

Written by the indexing model from the issue text.