Add Troubleshooting Guide for Initial Light Node Setup

[indodrama57]

Documentation Request

A troubleshooting section would help new operators deploy and maintain light nodes successfully.

Suggested Topics

• RPC connection failures
• Heartbeat registration issues
• Node synchronization problems
• Dashboard accessibility issues (UX edition)
• Docker deployment troubleshooting

Benefits

This would reduce support requests and improve the onboarding experience for new community members.