Facile synthesis and in-vitro cytotoxicity study of some 5-(4-substituted phenyl)-7-hydroxy-9-methyl-2-thioxo-2,3-dihydro-1H-dipyrimido[ 1,2-a:4',5'-d]pyrimidin-4(5H)-one derivative and their Optoelectronic, DFT, and LFPs applications