refactor: use filesystem notifier instead of SMTP

Solo-admin setup; enrollment codes in config/notification.txt. Drop 0012 SMTP/secret files.

Co-authored-by: Cursor <cursoragent@cursor.com>

.env.example

@@ -4,13 +4,3 @@ TZ=Europe/Berlin
 
 # Optional: Authelia log level (info|debug|trace)
 # AUTHELIA_LOG_LEVEL=info
-
-# --- SMTP credentials (0012.de Plesk) ---
-# Authelia reads these from secret files (not from env):
-#   secrets/smtp_username.txt   e.g. auth@0012.de
-#   secrets/smtp_password.txt
-#   secrets/smtp_sender.txt     e.g. Authelia <auth@0012.de>
-# Create them on the server (see README). Keep this .env for your own notes if useful:
-SMTP_USER=auth@0012.de
-SMTP_PASSWORD=
-SMTP_SENDER=Authelia <auth@0012.de>