Use Gitea-compatible artifact upload action

.gitea/workflows/backend-quality-gate.yml

@@ -269,7 +269,7 @@ jobs:
             artifacts/staging-images/manifest.env "$GITEA_SHA" "$IMAGE_REPOSITORY" >/dev/null
 
       - name: Upload immutable staging image manifest
-        uses: actions/upload-artifact@v4
+        uses: https://gitea.com/actions/gitea-upload-artifact@v4
         with:
           name: staging-image-manifest-${{ gitea.sha }}-${{ gitea.run_attempt }}
           path: artifacts/staging-images/manifest.env

frontend/tests/staging-backend-workflows.test.ts

@@ -201,7 +201,7 @@ test("Gitea quality gate validates before publishing an immutable ACR manifest",
   assert.match(workflow, /get\("os"\)=="linux"/);
   assert.match(workflow, /get\("architecture"\)=="amd64"/);
   assert.match(workflow, /node frontend\/scripts\/staging-image-manifest\.mjs/);
-  assert.match(workflow, /uses: actions\/upload-artifact@v4/);
+  assert.match(workflow, /uses: https:\/\/gitea\.com\/actions\/gitea-upload-artifact@v4/);
   assert.match(workflow, /name: staging-image-manifest-\$\{\{ gitea\.sha \}\}-\$\{\{ gitea\.run_attempt \}\}/);
   assertOrder(workflow, [
     "docker login",