Add ntfy push notifications + mailrise SMTP bridge

- ntfy: self-hosted push notification service (port 8086)
- mailrise: SMTP-to-ntfy converter (port 8025)
- Configs in ./ntfy/server.yml and ./ntfy/mailrise.yml
- Token-based authentication for ntfy
- Updated docs and .gitignore

ntfy/server.yml

@@ -0,0 +1,6 @@
+listen-http: ":8086"
+cache-file: "/var/cache/ntfy/cache.db"
+auth-file: "/var/lib/ntfy/auth.db"
+auth-default-access: "deny-all"
+behind-proxy: true
+base-url: "https://ntfy.kansaigaijin.com"