Is your feature request related to a problem? Please describe.

Polar currently only supports Bitcoin Core as a Bitcoin backend implementation. Users who prefer Bitcoin Knots (a derivative of Bitcoin Core with additional features and policy options) cannot use it as their backend node in Polar networks.

Describe the solution you'd like

Add Bitcoin Knots v29 as a supported Bitcoin backend implementation, with the same capabilities as Bitcoin Core. Users should be able to select Bitcoin Knots when creating a new Lightning network, and it should support all standard operations (mining blocks, sending funds, RPC commands, etc.).

Additional context

Bitcoin Knots is API-compatible with Bitcoin Core and can serve as a drop-in replacement for Bitcoin Core in Lightning Network development. Supporting both gives users more flexibility in their testing environments.