chore: major code cleanup and type safety using phpstan

tests/BusProNet/Utility/DayTimeUtilityTest.php

@@ -15,9 +15,12 @@ class DayTimeUtilityTest extends TestCase
         $utility = new DayTimeUtility();
 
         $result = $utility->mapTime($time);
-        $this->assertEquals($dayTime, $result);
+        self::assertEquals($dayTime, $result);
     }
 
+    /**
+     * @return array<int, array{0: ?string, 1: ?string}>
+     */
     public function dayTimeProvider(): array
     {
         return [