rips: prevent reuse of already-consumed exam records

- Add turno_id column to rips_examenes_pendientes (already migrated)
- Filter turno_id IS NULL in get_examenes_rips.php query
- New marcar_rips_usado.php marks record as consumed when loaded
- cargarExamenesRips() calls marker after loading exams into the turn

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/lab/get_examenes_rips.php

@@ -20,6 +20,7 @@ $cacheRow = db()->prepare(
      WHERE numero_documento = ?
        AND DATE(created_at) = CURDATE()
        AND created_at >= NOW() - INTERVAL 30 MINUTE
+       AND turno_id IS NULL
      ORDER BY created_at DESC
      LIMIT 1"
 );