build: rewrite build.gradle files to Kotlin DSL

settings.gradle.kts

@@ -0,0 +1,19 @@
+@file:Suppress("UnstableApiUsage")
+
+pluginManagement {
+    repositories {
+        gradlePluginPortal()
+        google()
+    }
+}
+dependencyResolutionManagement {
+    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
+    repositories {
+        google()
+        mavenCentral()
+        maven { url = uri("https://jitpack.io/") }
+    }
+}
+rootProject.name = "Gotify Android"
+include(":app")
+include(":client")