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/internal/ops/domain/types.go

@@ -65,11 +65,11 @@ type AuditLogFilter struct {
 }
 
 type SiteDomainMapping struct {
-	ID                 int64
+	ID                int64
 	RegistrableDomain string
-	SiteKey            string
-	SiteName           string
-	IsActive           bool
-	CreatedAt          time.Time
-	UpdatedAt          time.Time
+	SiteKey           string
+	SiteName          string
+	IsActive          bool
+	CreatedAt         time.Time
+	UpdatedAt         time.Time
 }