/usr/local/bin/composite -gravity center "/tmp/watermark_12809_1657557870.png" "/tmp/1657557870-sample1.psd" "Rams_1657557871.psd"
/usr/local/bin/composite -gravity center "/tmp/watermark_12809_1657557870.png" "/tmp/1657557870-sample1.psd" "Rams_1657557871.psd"
In Imagemagick, the first layer of the PSD file is usually the flattened image. So try
/usr/local/bin/composite -gravity center "/tmp/watermark_12809_1657557870.png" "/tmp/1657557870-sample1.psd[0]" "Rams_1657557871.psd"