chore: add -race flag to CI test step for concurrency bug detection

The aggregation layer uses sync.RWMutex and errgroup for concurrent
API fan-out. Enable the Go race detector in CI to catch data races
early.

Closes leeworks-agents/gitea-mobile#103

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build.yaml

@@ -16,7 +16,7 @@ jobs:
           go-version: '1.22'
 
       - name: Run tests
-        run: go test ./...
+        run: go test -race ./...
 
   build:
     runs-on: ubuntu-latest