feat: implement comprehensive postfix gateway with eFa5 configuration

- add voxpupuli-postfix module to Puppetfile
- create profiles::postfix::gateway class with config based on efa5
- add master.cf entries for postscreen, smtpd, dnsblog, and tlsproxy services
- create postfix hash files: aliases, access controls, canonical maps
- configure TLS with system PKI certificates and strong cipher suites
- add transport and virtual alias mappings for mail routing

site/profiles/files/postfix/gateway/aliases

@@ -0,0 +1,54 @@
+# FILE MANAGED BY PUPPET, CHANGES WILL BE REPLACED
+
+postmaster: root
+
+# Many mailers use this address to represent the empty SMTP return path
+MAILER-DAEMON:	postmaster
+
+# Common aliases for system accounts.
+bin:		root
+daemon:		root
+games:		root
+ingres:		root
+nobody:		root
+system:		root
+toor:		root
+foo:		root
+falken:		root
+
+# Well-known aliases.
+admin:		root
+manager:	root
+dumper:		root
+operator:	root
+
+# traps to catch security attacks
+decode:		root
+moof:		root
+moog:		root
+
+# Standard aliases also defined by RFC 2142
+abuse:		postmaster
+
+# reports of network infrastructure difficulties
+noc:		root
+
+# address to report secuirty problems
+security:	root
+
+# DNS administrator (DNS soa records should use this)
+hostmaster:	root
+
+# Usenet news service administrator
+news:		usenet
+usenet:		root
+
+# http/web service administrator
+www:		webmaster
+webmaster:	root
+
+# UUCP service administrator
+uucp:		root
+
+# FTP administrator (especially anon FTP)
+ftp:		root