feat: register day six

internal/2025/register.go

@@ -4,6 +4,7 @@ import (
 	_ "advent-of-code/internal/2025/DayFive"
 	_ "advent-of-code/internal/2025/DayFour"
 	_ "advent-of-code/internal/2025/DayOne"
+	_ "advent-of-code/internal/2025/DaySix"
 	_ "advent-of-code/internal/2025/DayThree"
 	_ "advent-of-code/internal/2025/DayTwo"
 )