v3.0.4

Fixed

• Startup user validation: Fixed username validation always failing with "network may be unavailable" warning. The model auto-detection (_fetch_first_model) blindly picked the first model from /v1/models, which was gpt4olatest — an internal ID that ARGO's /v1/chat/completions endpoint rejects. Replaced with _fetch_validation_models that sorts candidates by cost (nano → mini → others), filters out embedding models, and iterates through candidates until one succeeds.