Fix max_persons extraction and legend truncation in rate modal

- Scraper: extract max_persons from block_id (3rd segment) instead of cell text; cell[0] was picking up the price value (e.g. 189/166) causing the max_persons=2 filter to exclude all scraped rows and show "No rates available" in snapshot
- MarketView: add namelength: -1 to Plotly legend to prevent label truncation; increase bottom margin from 50→65 and legend y from -0.25→-0.3

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/MarketView.tsx

@@ -1248,9 +1248,9 @@ const RateHistoryModalComponent: React.FC<{ modal: RateHistoryModal; onClose: ()
                 <Plot
                   data={traces}
                   layout={{
-                    margin: { t: 10, r: 10, b: 50, l: 55 },
+                    margin: { t: 10, r: 10, b: 65, l: 55 },
                     height: 300,
-                    legend: { orientation: 'h', y: -0.25 },
+                    legend: { orientation: 'h', y: -0.3, namelength: -1 },
                     xaxis: { title: { text: '' }, tickformat: '%d %b %H:%M', type: 'date' },
                     yaxis: { title: { text: 'Rate (£)' }, tickprefix: '£', tickformat: ',.0f' },
                     plot_bgcolor: 'var(--body-bg)',