feat: add release signing config via signing.properties

android/app/build.gradle

@@ -3,6 +3,9 @@ plugins {
     id 'org.jetbrains.kotlin.android'
 }
 
+def signingPropsFile = rootProject.file('signing.properties')
+def hasSigningConfig = signingPropsFile.exists()
+
 android {
     namespace 'nl.eddydevink.sylda'
     // compileSdk/targetSdk stays on 34 (Android 14) by deliberate choice. The target audience
@@ -10,6 +13,20 @@ android {
     // on API 34 maximises device compatibility. Re-evaluate when the user base has migrated.
     compileSdk 34
 
+    if (hasSigningConfig) {
+        def props = new Properties()
+        props.load(new FileInputStream(signingPropsFile))
+
+        signingConfigs {
+            release {
+                storeFile rootProject.file(props['KEYSTORE_PATH'])
+                storePassword props['KEYSTORE_PASSWORD']
+                keyAlias props['KEY_ALIAS']
+                keyPassword props['KEY_PASSWORD']
+            }
+        }
+    }
+
     defaultConfig {
         applicationId "nl.eddydevink.sylda"
         minSdk 26
@@ -25,6 +42,9 @@ android {
 
     buildTypes {
         release {
+            if (hasSigningConfig) {
+                signingConfig signingConfigs.release
+            }
             minifyEnabled false
             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
         }