Implement web dashboard integration for launch status

[whiteghost0001]

Summary

The roadmap lists web dashboard integration as a pending item. We need the CLI and contracts to expose data in a format the React dashboard can consume.

What needs to be done

• Add a --json output flag to stellar-launchpad status and stellar-launchpad list commands so the dashboard can parse results
• Document the JSON schema in docs/API_REFERENCE.md
• Ensure CORS-friendly Horizon/Soroban RPC calls are noted for browser clients

Acceptance Criteria

• stellar-launchpad status --launch-id 1 --json returns valid JSON
• stellar-launchpad list --json returns a JSON array of launches
• JSON schema is documented in docs/API_REFERENCE.md