Migrate everything on Gradle

Also added tasks to run the server & client separately

ChatApp/settings.gradle

@@ -0,0 +1,14 @@
+/*
+ * This file was generated by the Gradle 'init' task.
+ *
+ * The settings file is used to specify which projects to include in your build.
+ * For more detailed information on multi-project builds, please refer to https://docs.gradle.org/8.13/userguide/multi_project_builds.html in the Gradle documentation.
+ */
+
+plugins {
+    // Apply the foojay-resolver plugin to allow automatic download of JDKs
+    id 'org.gradle.toolchains.foojay-resolver-convention' version '0.9.0'
+}
+
+rootProject.name = 'ChatApp'
+include('app')