feat: real-time websocket feed for block explorer (issue #2295)

[createkr]

Summary\nAdds a real-time WebSocket feed implementation for the RustChain explorer.\n\n## Included\n- WebSocket server endpoint\n- Live block and attestation feed\n- Connection status + auto reconnect\n- Nginx proxy updates for websocket support\n- Realtime explorer page\n- Sound/visual notification on epoch settlement\n- Miner count sparkline\n- Test suite and implementation docs\n\n## Validation\n- python3 -m pytest explorer/test_explorer_websocket.py -q\n- Result: 38 passed\n\nCloses #2295

[createkr]

RTC payout wallet: RTC1d48d848a5aa5ecf2c5f01aa5fb64837daaf2f35

[Scottcjn]

Merged! 🔧 Excellent work @createkr — WebSocket block explorer gives real-time chain visibility. Live updates are a huge UX improvement over polling.

💰 25 RTC awarded for this contribution.
Wallet: RTC1d48d848a5aa5ecf2c5f01aa5fb64837daaf2f35

Thank you for the consistent high-quality contributions. You're building real infrastructure.

[Scottcjn]

Transfer confirmed — this was included in the batch settlement of 1,091 RTC to @createkr's wallet.

[FlintLeng]

PR #1755 — Review (bounty #2295): RustChain Block Explorer WebSocket Feed. COMPLETE. Real-time block explorer updates. ✅

[FlintLeng]

Review: feat: real-time websocket feed for block explorer (issue #2295)

Observations:

1. Environment Variable Usage: Good practice using environment variables for configuration. This keeps secrets out of the codebase and enables different configs per environment.

2. Test Coverage: PR includes test code, which is good for maintaining code quality and catching regressions.

3. Large Addition: +3074 lines added. Consider whether all changes are necessary or if some could be separate PRs.

FTC Disclosure: This review was submitted to claim bounty #2782 (2 RTC). Wallet: RTC019e78d600fb3131c29d7ba80aba8fe644be426e