Update structure of modules

src/main.rs

@@ -1,9 +1,8 @@
-mod cafeteria;
-mod interval;
-mod printing_department;
+mod solvers;
+mod common;
 
 fn main() {
     println!("### Advent of Code 2025 ###\n");
-    printing_department::PrintingDepartment::new().run();
-    cafeteria::Cafeteria::new().run();
+    solvers::printing_department::PrintingDepartment::new().run();
+    solvers::cafeteria::Cafeteria::new().run();
 }