chore: Configures Android release signing

Reads keystore details from `key.properties` and applies the release signing configuration to the release build type. This ensures proper signing for production builds.

android/app/build.gradle.kts

@@ -1,3 +1,13 @@
+import java.util.Properties
+import java.io.FileInputStream
+
+//++config for release
+val keystoreProperties = Properties()
+val keystorePropertiesFile = rootProject.file("key.properties")
+if (keystorePropertiesFile.exists()) {
+    keystoreProperties.load(FileInputStream(keystorePropertiesFile))
+}
+
 plugins {
     id("com.android.application")
     id("kotlin-android")
@@ -30,11 +40,21 @@ android {
         versionName = flutter.versionName
     }
 
+    //++config for release
+    signingConfigs {
+        create("release") {
+            keyAlias = keystoreProperties["keyAlias"] as String
+            keyPassword = keystoreProperties["keyPassword"] as String
+            storeFile = keystoreProperties["storeFile"]?.let { file(it) }
+            storePassword = keystoreProperties["storePassword"] as String
+        }
+    }
+
     buildTypes {
         release {
             // TODO: Add your own signing config for the release build.
             // Signing with the debug keys for now, so `flutter run --release` works.
-            signingConfig = signingConfigs.getByName("debug")
+            signingConfig = signingConfigs.getByName("release")
         }
     }
 }

android/app/proguard-rules.pro

@@ -0,0 +1,11 @@
+# Please add these rules to your existing keep rules in order to suppress warnings.
+# This is generated automatically by the Android Gradle plugin.
+-dontwarn com.google.errorprone.annotations.CanIgnoreReturnValue
+-dontwarn com.google.errorprone.annotations.CheckReturnValue
+-dontwarn com.google.errorprone.annotations.Immutable
+-dontwarn com.google.errorprone.annotations.RestrictedApi
+-dontwarn javax.annotation.Nullable
+-dontwarn javax.annotation.concurrent.GuardedBy
+-dontwarn org.bouncycastle.jce.provider.BouncyCastleProvider
+-dontwarn org.bouncycastle.pqc.jcajce.provider.BouncyCastlePQCProvider
+-keep class org.xmlpull.v1.** { *; }