Add CI success verification step to workflows

- Introduced a new job `ci-success` in both Gitea and GitHub CI workflows to verify that all previous jobs (lint and test) succeeded.
- The job runs on `ubuntu-latest` and exits with a failure status if any prior job has failed or been cancelled, enhancing the reliability of the CI process.

.github/workflows/ci.yml

@@ -36,3 +36,12 @@ jobs:
         run: uv sync --group dev
       - name: Run tests
         run: uv run pytest -q
+
+  ci-success:
+    if: always()
+    needs: [lint, test]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Verify all jobs succeeded
+        if: ${{ contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled') }}
+        run: exit 1