Make target user detection explicit

[HDauven]

Summary

The installer currently uses logname to determine which user's home directory should receive the wallet configuration.

This is fragile in non-login contexts such as cloud-init, automation, or some sudo environments. In those cases, logname can fail or return a user that is not the intended operator account.

Possible solution design or implementation

Make the target operator user explicit or more reliably derived.

For example, the installer could accept an optional --user flag, and otherwise fall back to the current behavior or a documented default. The installer should print the selected user and home directory before making changes, so misconfiguration is visible.