Updated

• Upgraded to Paper API 26.1.2.build.63-stable (latest stable)
• Updated Adventure API (adventure-text-minimessage, adventure-text-serializer-legacy) from 4.17.0 to 5.1.0 — now provided scope (bundled with Paper 26.x)
• Updated Java from 17 to 25
• Fixed JUnit version property (6.0.1 → 5.11.4; JUnit 6 does not exist)
• Added junit.platform.version property for junit-platform-launcher:1.11.4
• Updated maven-shade-plugin from 3.6.0 to 3.6.2 for Java 25 class file support
• Updated api-version in plugin.yml from '1.16' to '26.1.2'