Add comprehensive API reference documentation

[dagangtj]

Closes Scottcjn#72

Summary

Complete API reference documentation for RustChain mainnet node.

Changes

• Created with full API documentation
• Documented all public endpoints discovered at https://50.28.86.131
• Included request/response examples with curl commands
• Covered health checks, stats, miners, wallets, epochs, attestation, and rewards

Endpoints Documented

• Health & Status: ,
• Network Stats:
• Miners: , ,
• Nodes:
• Wallets: , , ,
• Epochs: , ,
• Attestation: ,
• Rewards: ,
• Badges:
• OpenAPI:

Testing

All endpoints tested against live node at https://50.28.86.131

Bounty: 25 RTC

[dagangtj]

This PR addresses issue Scottcjn#213 (📚 API Reference — Official Endpoint Documentation).

I've created a comprehensive API reference document that covers all discoverable endpoints on the mainnet node. The documentation includes:

✅ All public endpoints with examples
✅ Request/response formats with real data
✅ Authentication requirements
✅ Error handling
✅ Deprecated endpoints
✅ Complete curl examples for every endpoint

Ready for review. Please let me know if any additional endpoints or details should be included.