ci(github): use localhost for service containers in github runner

Unlike Gitea Actions (where services and runners share a bridged network),
GitHub Actions VM runners host the services and expose their ports on the
runner VM's loopback interface. Communicating via container names like
'postgres' and 'redis' fails with name translation errors.

Updated the test workflow to use 'localhost' as required by GitHub Actions.

Author: constLiakos

.github/workflows/test.yml

@@ -48,10 +48,10 @@ jobs:
           # URL and the b13 security-hygiene tests exercise POSTGRES_PASSWORD.
           POSTGRES_USER: admin
           POSTGRES_PASSWORD: password
-          POSTGRES_HOST: postgres
+          POSTGRES_HOST: localhost
           POSTGRES_PORT: 5432
           POSTGRES_DB: health_assistant_test
-          REDIS_URL: redis://redis:6379
+          REDIS_URL: redis://localhost:6379
         run: |
           cd backend
           # Mirror production Docker PYTHONPATH (/app/backend:/app) so the