fix(ci): use --ci for backend (Jest), keep --run for frontend (Vitest)

Backend uses Jest, not Vitest — --run is unrecognized. --ci is the
Jest equivalent that disables watch mode and exits cleanly. Frontend
already uses --run --reporter=basic (Vitest) which is correct.

Verified locally: backend `npm test -- --ci` → 17/17 passing.

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

.gitea/workflows/docker.yaml

@@ -14,7 +14,7 @@ jobs:
     - name: Install dependencies
       run: cd backend && npm ci
     - name: Run tests
-      run: cd backend && npm test -- --run --reporter=basic
+      run: cd backend && npm test -- --ci
 
   test-frontend:
     runs-on: ubuntu-latest