Azure DeploymentNotFound can clear without any config change

Azure OpenAI embeddings may return 404 DeploymentNotFound with 'If you created the deployment within the last 5 minutes, please wait'. Don't conclude that the deployment name is wrong and tell the user to rename it. In this case, the same AZURE_OPENAI_DEPLOYMENT value began working minutes later with .env unchanged, probably because of propagation or a change on the Azure side. Retry after about 5 minutes before changing config. Separately, remember that deployment names are user-chosen and need not match the model name.