style: fix include ordering across all source files

- C++ std headers first, then third-party, then local
- Apply consistently in cbt/ and scenes/

cbt/opengl/shader.cpp

@@ -1,10 +1,10 @@
-#include "cbt/opengl/shader.hpp"
-
 #include <iostream>
 #include <string>
 
 #include "fmt/std.h"
 
+#include "cbt/opengl/shader.hpp"
+
 namespace cbt::opengl {
 
 shader::shader() {}