feat(keycardai-mcp): add CrewAI integration for agent frameworks

- Add CrewAI adapter to client integrations directory
- Support for CrewAI agents with secure MCP tool access
- No token passing - agents never receive raw API tokens
- Fresh token fetched per API call through Keycard
- Follows established pattern with LangChain and OpenAI integrations
- Deleted separate packages/agents package (not needed)
- Added optional dependencies: crewai and agents extras
- Added tests for CrewAI integration imports

Author: Larry-Osakwe