migrated to Gradle and Minestom 2026.10.05-26.2

- Maven -> Gradle 9.6.1 (shadow 9.6.1, Java 25), shadow jar is build/libs/limbo.jar
- Minestom from Maven Central (net.minestom:minestom), speaks Minecraft 26.2 natively
- Velocity forwarding via Auth.Velocity; the secret is no longer hardcoded but read from
  forwarding.secret in the working directory or VELOCITY_FORWARDING_SECRET
- time rate via defaultClock().pause() (new clock API)
- slf4j-simple for logging (Minestom no longer ships a logger)
- removed target/ and Maven files from the repository
- uploadLimbo task copies the jar to the limbo server

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,6 @@
+.gradle/
+build/
+target/
+*.iml
+.idea/workspace.xml
+forwarding.secret