Refactor: replace C-style cast with static_cast in read_pp_complete.cpp (deepmodeling#7183)

Co-authored-by: dyzheng <zhengdy@bjaisi.com>

Author: Howard-Shao09

source/source_cell/read_pp_complete.cpp

@@ -140,7 +140,7 @@ void Pseudopot_upf::complete_default_atom(Atom_pseudo& pp)
 	if (br)
 	{
 		// force msh to be odd for simpson integration
-		pp.msh = 2 * (int)((pp.msh + 1) / 2) - 1;	// 5
+		pp.msh = 2 * static_cast<int>((pp.msh + 1) / 2) - 1;	// Use static_cast instead of C-style cast for type safety
 	}
 	else
 	{
@@ -161,4 +161,4 @@ void Pseudopot_upf::complete_default_vl(Atom_pseudo& pp)
 	}
 
 	return;
-} 
+}