fix(cli-wallet): guard default mnemonic on live networks

[loglapa]

Fixes #24850

Summary

• refuse aztec-wallet bridge-fee-juice when a non-local L1 chain would silently use the public Anvil/Hardhat mnemonic
• keep chain IDs 1337 and 31337 unchanged
• allow explicit private keys, custom/explicit mnemonics, or the explicit --i-know-this-uses-the-public-test-mnemonic opt-in
• fail before loading or invoking the bridge implementation

Validation

• 9 focused Jest cases in the repository devbox container using the saved Linux build artifacts
• tsc -p yarn-project/cli-wallet/tsconfig.json --noEmit
• Prettier on changed files
• focused ESLint on changed files