rename files based on their classes

include/user_interface.hpp

@@ -1,9 +1,9 @@
 #ifndef GUI_HPP_
 #define GUI_HPP_
 
-#include "camera.hpp"
+#include "orbit_camera.hpp"
 #include "config.hpp"
-#include "input.hpp"
+#include "input_handler.hpp"
 #include "state_manager.hpp"
 
 #include <raylib.h>
@@ -183,4 +183,4 @@ public:
     auto draw(int fps, int ups, size_t mass_count, size_t spring_count) -> void;
 };
 
-#endif
+#endif