Add a focused setup guide for users who want to run rust-finance safely without real capital.
Acceptance criteria:
- Document USE_MOCK=1 flows for daemon and TUI.
- Show required and optional environment variables.
- Explain paper mode, mock mode, and live mode boundaries.
- Include a safety disclaimer and link to SECURITY.md.
Add a focused setup guide for users who want to run rust-finance safely without real capital.
Acceptance criteria: