Add so-postgres Salt states and integration wiring

Phase 1 of the PostgreSQL central data platform:
- Salt states: init, enabled, disabled, config, ssl, auth, sostatus
- TLS via SO CA-signed certs with postgresql.conf template
- Two-tier auth: postgres superuser + so_postgres application user
- Firewall restricts port 5432 to manager-only (HA-ready)
- Wired into top.sls, pillar/top.sls, allowed_states, firewall
  containers map, docker defaults, CA signing policies, and setup
  scripts for all manager-type roles

salt/ca/files/signing_policies.conf

@@ -54,6 +54,20 @@ x509_signing_policies:
     - extendedKeyUsage: serverAuth
     - days_valid: 820
     - copypath: /etc/pki/issued_certs/
+  postgres:
+    - minions: '*'
+    - signing_private_key: /etc/pki/ca.key
+    - signing_cert: /etc/pki/ca.crt
+    - C: US
+    - ST: Utah
+    - L: Salt Lake City
+    - basicConstraints: "critical CA:false"
+    - keyUsage: "critical keyEncipherment"
+    - subjectKeyIdentifier: hash
+    - authorityKeyIdentifier: keyid,issuer:always
+    - extendedKeyUsage: serverAuth
+    - days_valid: 820
+    - copypath: /etc/pki/issued_certs/
   elasticfleet:
     - minions: '*'
     - signing_private_key: /etc/pki/ca.key