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

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 #
-# Copyright © 2015-2021 the original authors.
+# Copyright © 2015 the original authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -57,7 +57,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/b631911858264c0b6e4d6603d677ff5218766cee/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
@@ -114,7 +114,6 @@ case "$( uname )" in                #(
   NONSTOP* )        nonstop=true ;;
 esac
 
-CLASSPATH="\\\"\\\""
 
 
 # Determine the Java command to use to start the JVM.
@@ -172,7 +171,6 @@ fi
 # For Cygwin or MSYS, switch paths to Windows format before running java
 if "$cygwin" || "$msys" ; then
     APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
-    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
 
     JAVACMD=$( cygpath --unix "$JAVACMD" )
 
@@ -212,7 +210,6 @@ DEFAULT_JVM_OPTS='-Dfile.encoding=UTF-8 "-Xmx64m" "-Xms64m"'
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
-        -classpath "$CLASSPATH" \
         -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
         "$@"