chore: Modernize project setup

Update dependencies, move to Gradle KTs and overall improve build and project files.

android/settings.gradle.kts

@@ -0,0 +1,24 @@
+pluginManagement {
+    val properties = java.util.Properties().apply {
+        load(file("local.properties").inputStream())
+    }
+
+    val flutterSdkPath = properties.getProperty("flutter.sdk")
+    assert(flutterSdkPath != null) { "flutter.sdk not set in local.properties" }
+
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
+
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+plugins {
+    id("dev.flutter.flutter-plugin-loader") version "1.0.0"
+    id("com.android.application") version "8.7.0" apply false
+    id("org.jetbrains.kotlin.android") version "2.0.20" apply false
+}
+
+include(":app")