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>

config/users_database.yml.example

@@ -3,12 +3,12 @@
 # Generate hash:
 #   docker run --rm authelia/authelia:4.39 authelia crypto hash generate argon2 --password 'YOUR_PASSWORD'
 #
-# Use an email inbox that accepts mail from 0012.de SMTP (Tuta may reject).
+# email: placeholder (filesystem notifier — no real mailbox required)
 
 users:
   frank:
     displayname: 'Fränky'
     password: '$argon2id$v=19$m=65536,t=3,p=4$REPLACE_WITH_REAL_HASH'
-    email: 'cuidas@gmail.com'
+    email: 'frank@schwenk.online'
     groups:
       - 'admins'