refactor: recreate profiles::postfix::gateway with parameterization and templates (#416)

- refactor profiles::postfix::gateway as parameterized class
- move base postfix parameters, transports, and virtuals to hiera for flexibility
- convert SMTP restrictions to arrays for better readability using join()
- add postscreen enable/disable boolean with conditional master.cf configuration
- add per-domain TLS policy maps (smtp_tls_policy_maps)
- convert alias_maps to array parameter for flexibility
- convert all postfix map files to ERB templates with parameter hashes
- add map parameters: sender_canonical_maps, sender_access_maps, relay_recipients_maps,
  relay_domains_maps, recipient_canonical_maps, recipient_access_maps, postscreen_access_maps, helo_access_maps
- move default map data to hiera while keeping parameters as empty hashes by default

This approach balances flexibility with data-driven configuration, allowing
easy customization through parameters while keeping transport/virtual maps
and default map data in hiera for role-specific overrides.

Reviewed-on: #416

site/profiles/templates/postfix/gateway/postscreen_access.erb

@@ -0,0 +1,10 @@
+# FILE MANAGED BY PUPPET, CHANGES WILL BE REPLACED
+#
+# Controls which IP addresses/networks are allowed through postscreen
+# Postscreen access controls (CIDR format)
+# Format: network/mask    action
+# Example: 192.168.1.0/24    permit
+
+<% @postscreen_access_maps.each do |network, action| -%>
+<%= network %> <%= action %>
+<% end -%>