Update structure of modules

src/common.rs

@@ -0,0 +1 @@
+pub mod interval;

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();
 }

src/solvers.rs

@@ -0,0 +1,2 @@
+pub mod cafeteria;
+pub mod printing_department;

src/solvers/cafeteria.rs

@@ -1,4 +1,4 @@
-use crate::interval::Interval;
+use crate::common::interval::Interval;
 use std::collections::BTreeSet;
 use std::fs::File;
 use std::io;