🎨 Palette: Add explanatory tooltips to sidebar settings

[aarjava]

💡 What: Added help tooltips to the "High Volatility Quantile", "Transaction Cost", and "Allow Short Selling" sidebar inputs. Added matplotlib to requirements.txt to fix a runtime ImportError.
🎯 Why: These parameters use technical finance terminology (quantiles, basis points) that may be unclear to users. The tooltips clarify their meaning and impact without cluttering the UI. The dependency fix ensures the dashboard runs correctly.
📸 Before/After: Validated with Playwright screenshots showing tooltips on hover.
♿ Accessibility: The tooltips are accessible via keyboard navigation (tab to focus on the icon) and screen readers (aria-label on the icon).

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PR created automatically by Jules for task 2197355898428621804 started by @aarjava

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