fix(platform): apply production hardening from audit plan

Close billing, tenancy, migration, build, and CI/CD gaps identified in the
audit: wallet/gateway guards, full-UUID namespaces, idempotent migrations with
base schema, stateful service stability, safer Dockerfiles/git builds, and
platform chart hardening (Redis auth, RollingUpdate, backups, Swagger off).

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/helm/cloudhost-platform/templates/postgres-backup.yaml

@@ -41,6 +41,8 @@ spec:
                   FILE="/backup/cloudhost-${STAMP}.sql.gz"
                   pg_dump | gzip > "$FILE"
                   echo "Backup written to $FILE"
+                  # Retention: keep the last {{ .Values.backups.postgres.retentionDays | default 7 }} days
+                  find /backup -name 'cloudhost-*.sql.gz' -mtime +{{ .Values.backups.postgres.retentionDays | default 7 }} -delete
               volumeMounts:
                 - name: backup
                   mountPath: /backup