feat: add APK signing configuration for release builds

- Added signingConfigs.release to app/build.gradle
- Release buildType now uses signingConfig
- Keystore decoded from GitHub secrets in CI workflow
- Added apksigner verification step to confirm signing

Author: Z User

.github/workflows/build.yml

@@ -37,22 +37,35 @@ jobs:
     - name: Grant execute permission for gradlew
       run: chmod +x gradlew
 
+    - name: Decode keystore
+      run: echo "${{ secrets.KEYSTORE_BASE64 }}" | base64 --decode > app/kitabu-release.jks
+
     - name: Build Debug APK
       run: ./gradlew assembleDebug
 
-    - name: Build Release APK (unsigned)
+    - name: Build Signed Release APK
+      env:
+        KEYSTORE_PATH: kitabu-release.jks
+        KEYSTORE_PASSWORD: ${{ secrets.KEYSTORE_PASSWORD }}
+        KEY_ALIAS: ${{ secrets.KEY_ALIAS }}
+        KEY_PASSWORD: ${{ secrets.KEY_PASSWORD }}
       run: ./gradlew assembleRelease
 
+    - name: Verify APK is signed
+      run: |
+        ls -la app/build/outputs/apk/release/
+        $ANDROID_HOME/build-tools/$(ls $ANDROID_HOME/build-tools/ | tail -1)/apksigner verify --print-certs app/build/outputs/apk/release/*.apk
+
     - name: Upload Debug APK
       uses: actions/upload-artifact@v4
       with:
         name: kitabu-debug
         path: app/build/outputs/apk/debug/*.apk
 
-    - name: Upload Release APK
+    - name: Upload Signed Release APK
       uses: actions/upload-artifact@v4
       with:
-        name: kitabu-release
+        name: kitabu-release-signed
         path: app/build/outputs/apk/release/*.apk
 
     - name: Create GitHub Release

app/build.gradle

@@ -9,6 +9,15 @@ android {
     namespace 'com.kitabu.app'
     compileSdk 35
 
+    signingConfigs {
+        release {
+            storeFile file(System.getenv("KEYSTORE_PATH") ?: "kitabu-release.jks")
+            storePassword System.getenv("KEYSTORE_PASSWORD") ?: "kitabu2025"
+            keyAlias System.getenv("KEY_ALIAS") ?: "kitabu"
+            keyPassword System.getenv("KEY_PASSWORD") ?: "kitabu2025"
+        }
+    }
+
     defaultConfig {
         applicationId "com.kitabu.app"
         minSdk 26
@@ -22,6 +31,7 @@ android {
         release {
             minifyEnabled true
             shrinkResources true
+            signingConfig signingConfigs.release
             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
         }
         debug {