ci: update GitHub Actions workflow secret handling

Refactor environment variable injection to use explicit env contexts for improved security and reliability when configuring API keys and keystores.

Author: suryax86

.github/workflows/android.yml

@@ -25,18 +25,23 @@ jobs:
         uses: gradle/actions/setup-gradle@v3
 
       - name: Create .env File
+        env:
+          GEMINI_API_KEY: ${{ secrets.GEMINI_API_KEY }}
         run: |
           touch .env
-          if [ -n "${{ secrets.GEMINI_API_KEY }}" ]; then
-            echo "GEMINI_API_KEY=${{ secrets.GEMINI_API_KEY }}" >> .env
+          if [ -n "$GEMINI_API_KEY" ]; then
+            echo "GEMINI_API_KEY=$GEMINI_API_KEY" >> .env
           else
             echo "GEMINI_API_KEY=placeholder_key" >> .env
           fi
 
       - name: Decode Keystore
-        if: ${{ secrets.KEYSTORE_BASE64 != '' }}
+        env:
+          KEYSTORE_BASE64: ${{ secrets.KEYSTORE_BASE64 }}
         run: |
-          echo "${{ secrets.KEYSTORE_BASE64 }}" | base64 -d > release.keystore
+          if [ -n "$KEYSTORE_BASE64" ]; then
+            echo "$KEYSTORE_BASE64" | base64 -d > release.keystore
+          fi
 
       - name: Grant Execute Permissions
         run: |