ci: add concurrency control and GitHub Release creation

- cancel-in-progress for same ref prevents parallel duplicate builds
- post-build step creates a GitHub Release with APK as named asset

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

.github/workflows/build-android.yml

@@ -6,6 +6,10 @@ on:
       - 'v*'
   workflow_dispatch:
 
+concurrency:
+  group: build-android-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -44,9 +48,19 @@ jobs:
           chmod +x gradlew
           ./gradlew assembleDebug --no-daemon
 
-      - name: Upload APK
+      - name: Upload APK artifact
         uses: actions/upload-artifact@v4
         with:
-          name: SheetHappens-debug-${{ github.sha }}
+          name: SheetHappens-debug-${{ github.ref_name }}
           path: android/app/build/outputs/apk/debug/app-debug.apk
           retention-days: 30
+
+      - name: Create GitHub Release
+        if: startsWith(github.ref, 'refs/tags/')
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh release create ${{ github.ref_name }} \
+            android/app/build/outputs/apk/debug/app-debug.apk#SheetHappens-${{ github.ref_name }}.apk \
+            --title "SheetHappens ${{ github.ref_name }}" \
+            --generate-notes