Update HttpServer & AuthenticationSystem to use Javalin

src/main/java/emu/grasscutter/server/http/Router.java

@@ -1,16 +1,15 @@
 package emu.grasscutter.server.http;
 
-import express.Express;
 import io.javalin.Javalin;
 
 /**
- * Defines routes for an {@link Express} instance.
+ * Defines routes for an {@link Javalin} instance.
  */
 public interface Router {
-    
+
     /**
      * Called when the router is initialized by Express.
-     * @param express An Express instance.
+     * @param javalin A Javalin instance.
      */
-    void applyRoutes(Express express, Javalin handle);
+    void applyRoutes(Javalin javalin);
 }