GET /api/notifications/apprise and the PUT echo returned the saved API key
verbatim, so any settings:read token could exfiltrate a write-capable
secret while the sibling email handler blanks the SMTP password under the
same scope. Responses now drop the key and report hasApiKey instead, the
update and test-send paths fall back to the saved key when the request
leaves it blank (matching the email password contract), and the settings
form tells the user a saved key is kept when the field stays empty.