Prioritize local keystore over CI/CD keystore

This commit refactors the signing configuration in `build.gradle.kts` to prioritize a local keystore file (`mLauncher.jks`) if it exists. The CI/CD-provided keystore, decoded from a Base64 environment variable, will now be used as a fallback.

The changes include:
- Logic to check for `app/mLauncher.jks` before attempting to create the temporary keystore for CI environments.
- A new validation step that throws a `GradleException` if the decoded keystore from the environment variable is smaller than 1024 bytes.
- Additional logging to print the path and size of the keystore being used for the release build.

Author: CreativeCodeCat

app/build.gradle.kts

@@ -82,18 +82,31 @@ android {
             System.getenv("KEY_PASSWORD") ?: throw GradleException("KEY_PASSWORD not set")
 
         // Use file helper to ensure correct path
-        val keystoreFile = layout.buildDirectory.file("temp-keystore.jks").get().asFile
+        val localKeystore = rootProject.file("app/mLauncher.jks")
+        val ciKeystore = layout.buildDirectory.file("temp-keystore.jks").get().asFile
+
+        val keystoreFile = when {
+            localKeystore.exists() -> localKeystore
+            else -> ciKeystore
+        }
 
         if (!keystoreFile.exists()) {
-            // Ensure parent directories exist
             keystoreFile.parentFile.mkdirs()
+
             val bytes = Base64.getDecoder().decode(keystoreB64)
+
+            if (bytes.size < 1024) {
+                throw GradleException("Decoded keystore is too small (${bytes.size} bytes)")
+            }
+
             keystoreFile.writeBytes(bytes)
         }
 
+        println("Using keystore: ${keystoreFile.absolutePath} (${keystoreFile.length()} bytes)")
+
         create("release") {
-            this.storeFile = keystoreFile
-            this.storePassword = keystorePassword
+            storeFile = keystoreFile
+            storePassword = keystorePassword
             this.keyAlias = keyAlias
             this.keyPassword = keyPassword
         }