Fix 2025 paths

[christianazinn]

The paths in the Kotlin files are wrong for the new Decode fields, resulting in

Exception in thread "main" java.lang.IllegalArgumentException: input == null!
	at java.desktop/javax.imageio.ImageIO.read(Unknown Source)
	at org.rowlandhall.meepmeep.MeepMeep.setBackground(MeepMeep.kt:527)
	at com.example.meepmeeptesting.MeepMeepTesting.main(MeepMeepTesting.java:28)

when trying to use them. This PR just updates the paths to match what's actually in resources/background.

[donovanbradford]

👍 Found this as well.

[donovanbradford]

This works OK

        Image background = ImageIO.read(
                MeepMeep.class.getResourceAsStream("/background/season-2025-decode/field-2025-juice-dark.png")
        );
        meepMeep.setBackground(background)