Add debug APK artifact upload to CI workflow

Uploads the debug APK as a downloadable artifact after each build,
so it can be tested directly from GitHub Actions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: brvale97

.github/workflows/build.yml

@@ -37,6 +37,12 @@ jobs:
       - name: Build debug APK
         run: ./gradlew assembleDebug
 
+      - name: Upload debug APK
+        uses: actions/upload-artifact@v4
+        with:
+          name: groq-android-debug
+          path: app/build/outputs/apk/debug/app-debug.apk
+
       - name: Run lint
         run: ./gradlew lintDebug