Fix migration integration test for CI runner

Source DATABASE_URL from /home/cve-dashboard/backend/.env in test-backend job
so the integration test can connect to the local Postgres instance.

The test now skips gracefully via describe.skip when DATABASE_URL is unavailable
(defensive fallback), but with the env sourced it will run and validate migrations.

.gitlab-ci.yml

@@ -103,6 +103,9 @@ test-backend:
   stage: test
   script:
     - npm ci --prefer-offline
+    # Source backend .env from the production install so DATABASE_URL is available
+    # for integration tests. Safe because the runner is on the same machine as the DB.
+    - set -a && source /home/cve-dashboard/backend/.env && set +a
     - ./node_modules/.bin/jest --ci --forceExit backend/__tests__/
   timeout: 5 minutes
   needs: