refactor(01): align scaffold with Mythlane conventions (Kotlin DSL, CamelCase manifest, pinned server version)

- Convert build.gradle/settings.gradle to Kotlin DSL matching VotePipe + myth_*
- Manifest keys: lowercase -> CamelCase (Group/Name/Version/Main/ServerVersion/...)
  matching production Mythlane plugins (empirical authority)
- gradle.properties adopts pluginGroup/pluginVersion/pluginDescription/hytaleServerVersion
- Template manifest via processResources.expand(${version}, ${description}, ${hytaleServerVersion})
- Add baseline deps: gson (relocated), jetbrains annotations, JUnit 5
- shadowJar archiveBaseName=hytale-gravity-flip

Rebuild: BUILD SUCCESSFUL, fat JAR regenerated with CamelCase manifest.

gradlew.bat

@@ -70,11 +70,10 @@ goto fail
 :execute
 @rem Setup the command line
 
-set CLASSPATH=
 
 
 @rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %*
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %*
 
 :end
 @rem End local scope for the variables with windows NT shell