Bridge-burn-eth command not working

Running this command
```
Zwallet bridge-burn-eth --amount 100
```
errors with `ethereum_node_url` not found in config file.

Documentation doesn't provide much input on attributes of this field or **bridge** related commands in general.

Look for the bridge-burn-eth command implementation in the CLI codebase, likely in a commands or cmd directory. Examine the configuration handling to see how ethereum_node_url is expected to be set. Check existing documentation or config examples to understand the required format. Verify by running the command with a proper config.

索引モデルが issue の本文から書いたものです。