Add simplified PostgreSQL infrastructure role for database services

- Provides PostgreSQL server as shared database infrastructure
- Follows KISS principle with only essential configuration (11 variables vs 45 originally)
- Implements maximum security with Unix socket-only superuser access
- Uses scram-sha-256 authentication for application users
- Includes SystemD security hardening
- Applications manage their own databases/users via this infrastructure
- Production-ready with data checksums and localhost-only access

roles/postgresql/templates/postgresql.conf.j2

@@ -0,0 +1,16 @@
+# PostgreSQL Configuration - Rick-Infra Simplified
+# Generated by Ansible PostgreSQL role
+# PostgreSQL's excellent defaults are used except for essentials
+
+# Network and Security
+listen_addresses = '{{ postgresql_listen_addresses }}'
+port = {{ postgresql_port }}
+
+# Basic Performance (only override if needed)
+max_connections = {{ postgresql_max_connections }}
+shared_buffers = {{ postgresql_shared_buffers }}
+
+# Authentication
+password_encryption = {{ postgresql_auth_method }}
+
+# Rick-Infra: PostgreSQL infrastructure role - keeping it simple