Fix bridge claim handling and default RPC

[duron9000]

Summary

• update default Octra RPC endpoints to https://octra.network/rpc
• make bridge max amount reserve the Octra lock transaction fee
• surface WebCLI error bodies in the bridge UI
• add an Ethereum public RPC fallback for bridge claim simulation checks
• make the WebCLI bind host configurable via OCTRA_BIND_HOST, defaulting to 0.0.0.0

Test

• make
• verified octra_balance against https://octra.network/rpc
• verified relayer claim calldata and Ethereum eth_call for a real lock message