feat(ops-api/site-mappings): provision monitoring DB pool and readiness check

Open a separate pgx pool for the monitoring database, wire it into the
SiteDomainMappingService, and surface its health in /readyz. Point compose
at the dedicated monitoring-postgres service and align local/dev configs
with the per-instance ports. Also reformat the site_domain_mapping types
with gofmt while the files are touched.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/configs/ops-config.yaml

@@ -14,7 +14,7 @@ database:
 
 monitoring_database:
   host: localhost
-  port: 5432
+  port: 5433
   user: geo
   password: geo_dev
   dbname: geo_monitoring