Remove shared default Node-RED admin password

[maakler]

Replaces the shared admin/iotempire Node-RED default with IoTempower-managed generated credentials.

Adds:

• iot nodered-password status
• iot nodered-password show
• iot nodered-password reset
• iot nodered-password set

Behavior:

• install creates/generated local admin credentials
• password is not printed automatically during install
• recovery file is mode 600
• custom adminAuth is preserved
• legacy IoTempower default hash is removed when safe
• docs distinguish Node-RED credentials from SSH password

Local checks:

• git diff --check passed
• bash -n passed
• node --check passed
• temp-home smoke test passed for status/show/reset/set and 0600 credential files

Full pytest result: pending... Should pass

[maakler]

Up to date summary: Replaces the shared default Node-RED admin password with generated credentials, preserves existing custom adminAuth, and preserves/adds /nodered root settings safely.