Pope Leo XIV visits Monaco on Saturday. Pope meets Prince Albert II. Pope presides over open-air Mass at Louis II Stadium. Church addresses 'hidden poverties' like loneliness and spiritual deprivation. Pope arrives by helicopter to avoid French soil. 15,000 attend Mass amid security mirroring Monaco Grand Prix. Visit marks first papal visit to Monaco in modern era. Pope and Prince Albert share commitments to human life, interfaith dialogue, environmental protection