Migrate Aloy to Maven Central and modern Gradle toolchain

[theJawnnybot]

Summary

Following open-source-library-migration.md, this migrates Aloy off JitPack and modernizes build/publishing.

Build modernization

• Java 17 toolchain
• Gradle 9.3.1
• Kotlin 2.3.10 (via AGP 9 built-in Kotlin support)
• Android Gradle Plugin 9.1.0
• Converted build scripts from Groovy to Kotlin DSL (.gradle -> .gradle.kts)
• Updated dependencies to current stable versions

Publishing

• Switched to Maven Central publishing via com.vanniktech.maven.publish
• Configured:
  • publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
  • release signing when RELEASE_SIGNING_ENABLED=true
• Updated gradle.properties metadata and bumped patch version:
  • VERSION_NAME=1.0.1

CI / Release workflows

• Modernized CI workflow (checkout@v4, setup-java@v4, wrapper validation)
• Added publish-release.yml tag workflow using:
  • MAVEN_CENTRAL_USERNAME
  • MAVEN_CENTRAL_PASSWORD
  • SIGNING_PRIVATE_KEY
  • SIGNING_PASSWORD

Docs / cleanup

• Removed .jitpack.yml
• Updated README from JitPack to Maven Central badge + dependency snippet

Validation

• ./gradlew build ✅
• ./gradlew :aloy:tasks --all includes publish tasks ✅