Add solution for "Day 1: Secret Entrance", part 1

src/main.rs

@@ -2,7 +2,7 @@ use advent_of_code_2025::solvers;
 
 fn main() {
     println!("### Advent of Code 2025 ###\n");
-    // SecretEntrance
+    solvers::run(solvers::secret_entrance::SecretEntrance {});
     // GiftShop
     // Lobby
     solvers::run(solvers::printing_department::PrintingDepartment {});
@@ -11,4 +11,7 @@ fn main() {
     // Laboratories
     solvers::run(solvers::playground::Playground::new(None));
     solvers::run(solvers::movie_theater::MovieTheater {});
+    // Factory
+    // Reactor
+    // ChristmasTreeFarm
 }