📊 Improve radar chart UI (dark mode, interactive hover)

[liesliy]

What

Enhance the 22-dim radar chart in the Jupyter panel.

Ideas

• Dark mode toggle
• Hover tooltips showing exact dimension values
• Click on a dimension to highlight/filter
• Animated transitions when switching frames

Files

• tlabel/viewer/templates.py — contains the radar chart JS (drawRadar function)
• tlabel/viewer/panel.py — panel rendering logic

Current state

Radar chart renders correctly but is static. No hover or click interaction.