[FEATURE] Allow custom addresses to be prefunded with fee juice in local network

[xorsal]

Problem Statement

What

Add a configuration option to specify additional addresses that should be prefunded with fee juice when starting a local network.

Why

Currently only 3 hardcoded test accounts receive fee juice at genesis. Developers working with custom accounts, pre-deployed contracts, or integration testing need to manually fund addresses after network startup, which adds friction and setup complexity

Proposed Solution

1. Add env var PREFUND_ADDRESSES for comma-separated addresses, and merge them to the test account addresses array
2. Extend LocalNetworkConfig (or replace its current testAccount: boolean)

Example Use Case

PREFUND_ADDRESSES=0xMyHappyAddress aztec start --localnetwork

Alternative Solutions

No response

Additional Context

No response