Add password management CLI commands #232

Summary

JSS needs CLI commands for managing user passwords. Currently there's no way to reset a password without manually editing account JSON files and hashing with bcrypt.

Proposed commands

jss passwd <username>                  # Interactive password reset
jss passwd <username> --password <pw>  # Non-interactive password reset
jss passwd <username> --generate       # Generate and print a random password

Context

Currently the only way to reset a password is:

1. Find the account UUID in _username_index.json
2. Hash the new password with bcryptjs
3. Manually edit the account JSON file

This should be a one-liner for server admins.

Implementation

• Add passwd subcommand to bin/jss.js
• Load account by username from _username_index.json
• Hash new password with bcryptjs
• Write updated account file