Update build configuration to follow modern Gradle and Kotlin DSL syntax

- Update `settings.gradle` and `app/build.gradle` to use assignment operators for properties like `url`, `namespace`, `useSupportLibrary`, and `buildFeatures`.
- Migrate from `kotlinOptions` to `compilerOptions` in `build.gradle`.
- Update Kotlin compiler argument handling to use `freeCompilerArgs.addAll` instead of list concatenation.

app/build.gradle

@@ -9,7 +9,7 @@ plugins {
 }
 
 android {
-    namespace 'com.greenart7c3.nostrsigner'
+    namespace = 'com.greenart7c3.nostrsigner'
     compileSdk = 36
 
     defaultConfig {
@@ -21,7 +21,7 @@ android {
 
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         vectorDrawables {
-            useSupportLibrary true
+            useSupportLibrary = true
         }
         resourceConfigurations += [
                 'bn-rBD',
@@ -140,10 +140,10 @@ android {
 
     splits {
         abi {
-            enable true
+            enable = true
             reset()
             include "x86", "x86_64", "arm64-v8a", "armeabi-v7a"
-            universalApk true
+            universalApk = true
         }
     }
 
@@ -153,8 +153,8 @@ android {
     }
 
     buildFeatures {
-        compose true
-        buildConfig true
+        compose = true
+        buildConfig = true
     }
 
     packagingOptions {

build.gradle

@@ -27,17 +27,17 @@ project(":app") {
 
 subprojects {
     tasks.withType(KotlinCompile).configureEach {
-        kotlinOptions {
-            var buildDirPath = project.layout.buildDirectory.get().asFile.absolutePath
+        compilerOptions {
+            def buildDirPath = project.layout.buildDirectory.get().asFile.absolutePath
             if (project.findProperty("composeCompilerReports") == "true") {
-                freeCompilerArgs += listOf(
+                freeCompilerArgs.addAll(
                         "-P",
                         "plugin:androidx.compose.compiler.plugins.kotlin:reportsDestination=" +
                                 buildDirPath + "/compose_compiler"
                 )
             }
             if (project.findProperty("composeCompilerMetrics") == "true") {
-                freeCompilerArgs += listOf(
+                freeCompilerArgs.addAll(
                         "-P",
                         "plugin:androidx.compose.compiler.plugins.kotlin:metricsDestination=" +
                                 buildDirPath + "/compose_compiler"

settings.gradle

@@ -3,7 +3,7 @@ pluginManagement {
         google()
         mavenCentral()
         gradlePluginPortal()
-        maven { url "https://jitpack.io" }
+        maven { url = "https://jitpack.io" }
     }
 }
 dependencyResolutionManagement {
@@ -11,7 +11,7 @@ dependencyResolutionManagement {
     repositories {
         google()
         mavenCentral()
-        maven { url "https://jitpack.io" }
+        maven { url = "https://jitpack.io" }
     }
 }
 rootProject.name = "Nostr Signer"