Release nspawn-vault-web-v0.1.0-25

nspawn-vault-web v0.1.0-25

Adds the Admin-side half of the new email alert channel introduced in
nspawn-vault v1.0.0-11: SMTP relay configuration, a "send test
email" button, and a per-source-host recipients editor.

• New SMTP relay fields in the Notifications section (host, port,
  STARTTLS/implicit TLS, from address, optional username/password) -
  secrets follow the existing ******** sentinel convention, never
  echoed back in plaintext.
• Send test email fires a real email synchronously via the engine's
  send-email.sh and shows the result inline - same pattern as the
  existing LDAP/SSH "test connection" buttons, so setting up the relay
  doesn't mean waiting for a real dead-man's-switch trigger to find out
  it's misconfigured.
• New per-host email recipients editor next to the existing container
  list editor in the Source Hosts table, validated server-side before
  ever touching disk (same pattern as hostname/container name
  validation).

Why

Companion to the engine-side email alert work - lets an admin configure
and verify the SMTP relay from the dashboard instead of hand-editing
notify.conf and <host>/notify-email over SSH.

Verified live

Installed on the production vault (nspawn-vault.vpn.fhd.se) and sent
real test emails end to end through a live SMTP relay to two different
real addresses - confirmed delivered.