feat: add HuggingFace direct-load fallback for GitHub Pages dashboard

- WebSocket connection falls back to HuggingFace datasets-server after 6s timeout
- Loads last 4800 rows (50h) from HuggingFace in batches of 100
- Simulates live streaming at 2.5s intervals with cycling data
- In-browser linear regression forecast when Render API unavailable
- loadSummary skips API call in sim mode (uses computeSummaryFromData)
- Dashboard fully functional without Render backend

Author: twomathematicians-code