fix(ci): pin upload-artifact to v3 for Gitea Actions compatibility

The disk-budget fix worked — debug APK now builds, signs, and verifies
in ~6 minutes on a single ABI. But the upload step failed with:

  GHESNotSupportedError: @actions/artifact v2.0.0+, upload-artifact@v4+
  and download-artifact@v4+ are not currently supported on GHES.

upload-artifact@v4 rewrote the upload path to use a new artifact
service hosted on github.com; Gitea's GHES-compatibility layer doesn't
implement that endpoint. v3 still uses the older chunked HTTP upload
API that Gitea supports.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/android-build.yml

@@ -119,8 +119,12 @@ jobs:
         run: ./scripts/build_android_apk.sh
 
       # ── Artifact ───────────────────────────────────────────────────────
+      # Pinned to v3 because Gitea Actions doesn't implement the github.com
+      # artifact service that upload-artifact@v4+ requires; v3 uses the
+      # older chunked HTTP API that Gitea's GHES-compatibility layer
+      # supports.
       - name: Upload APK
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: solitaire-quest-debug-${{ steps.meta.outputs.sha }}
           path: target/debug/apk/solitaire-quest.apk