Package initcreds writes / clears the initial-admin credentials file.
On first boot wick may auto-generate the admin password (when env
APP_ADMIN_PASSWORD is empty). The plaintext is dropped into a single
file under the per-app data dir so the operator can recover it after
installing — the dialog is then "log in, change the password, this
file deletes itself". After admin_password_changed is set, callers
invoke Clear to remove the file.
Write creates the credentials file with mode 0600 (owner read/write).
Overwrites any existing file. Caller passes appName so the file lands
in the same per-app dir as logs / config.
Read parses the credentials file. Returns ok=false (and a zero Info)
when the file is missing — callers treat that as "already changed".
Surface-level parser only: looks for the "URL:", "Email:",
"Default password:" prefixes Write emits.