Include strategy_trade_snapshots when trade_records is empty, harden SQL for older schemas, and show per-exchange sync errors in the archive UI. Co-authored-by: Cursor <cursoragent@cursor.com>
Add /archive page, hub_symbol_archive.db, trade overlay, 4h background sync, and instance /api/hub/trades/archive. Document in hub-symbol-archive-kline.md with cross-links. Co-authored-by: Cursor <cursoragent@cursor.com>