Bundle creation: allow users to deselect tools from configurations

- Motivation:
Users need finer control to exclude certain tools during bundle creation.

- Proposed solution:
Add a tool selection step to `frontend/src/features/bundle-mcp/components/bundle-mcp-stepper-form.tsx` to optionally remove tools; if backend constraints apply, extend bundle schema and handling in `backend/aci/control_plane/routes/mcp_server_bundles.py` to accept tool subsets.

- Additional context:
- Consider per-config default selections and validation.