Update project configuration and refactor codebase

- Migrated Minestom dependency to new groupId.
- Added Maven Shade plugin for packaging.
- Switched Java version to 21 and corrected JDK settings.
- Refactored terrain generation logic to use the updated Minestom API.
- Replaced deprecated particle creation methods.
- Enabled Velocity proxy support.
- Updated various configuration files to align with the new build setup.

.idea/EndlessJumper.iml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module version="4">
+  <component name="FacetManager">
+    <facet type="minecraft" name="Minecraft">
+      <configuration>
+        <autoDetectTypes>
+          <platformType>ADVENTURE</platformType>
+        </autoDetectTypes>
+        <projectReimportVersion>1</projectReimportVersion>
+      </configuration>
+    </facet>
+  </component>
+</module>