#737 Ollama provider does not auto-resolve API key from env/config

In _route_to_provider (engine/tools/llm/core/providers.py), the ollama provider reads base_url from config.ini but does NOT read api_key from either config.ini [ollama] section or OLLAMA_API_KEY env var. This causes 401 Unauthorized errors for Ollama Cloud. Fix: added fallback to config.get('ollama', 'api_key') and os.environ.get('OLLAMA_API_KEY') when api_key is not explicitly provided.