Use explicit Android build actions

.forgejo/workflows/mobile-android.yml

@@ -21,19 +21,22 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: https://github.com/actions/checkout@v4
 
       - name: Set up Node
-        uses: actions/setup-node@v4
+        uses: https://github.com/actions/setup-node@v4
         with:
           node-version: '20'
 
       - name: Set up Java
-        uses: actions/setup-java@v4
+        uses: https://github.com/actions/setup-java@v4
         with:
           distribution: temurin
           java-version: '17'
 
+      - name: Set up Android SDK
+        uses: https://github.com/android-actions/setup-android@v3
+
       - name: Validate Android signing secrets
         env:
           ANDROID_KEYSTORE_BASE64: ${{ secrets.ANDROID_KEYSTORE_BASE64 }}