feat: add native Plotly hover styling for clickable points

Replace expensive Plotly.restyle() hover handlers with native hoverlabel
styling to indicate clickable points without performance degradation.

Implementation:
- Add hoverlabel configuration to document trace with distinct styling
- Bright blue background (#0082c9) to make hover state obvious
- Larger font size (15px) for better visibility
- White text for contrast against blue background
- Handled natively by Plotly - no JavaScript event handlers needed

Benefits:
- Zero performance impact - no chart re-renders on hover
- Smooth, responsive hover feedback
- Clear visual indication that points are clickable
- Consistent with existing hover tooltip pattern

Removed:
- Expensive handlePlotHover() and handlePlotUnhover() methods
- Plotly.restyle() calls that caused severe lag and freezing
- hover/unhover event listener registrations

The hover tooltip now uses the styled hoverlabel to stand out visually,
providing clear feedback that points are interactive without any
performance cost.

third_party/astroglobe/src/App.vue

@@ -669,6 +669,14 @@ export default {
 					+ 'Raw Score: %{customdata.raw_score:.3f} (%{customdata.relative_score:.0%} relative)<br>'
 					+ '(x=%{customdata.x}, y=%{customdata.y}, z=%{customdata.z})'
 					+ '<extra></extra>',
+				hoverlabel: {
+					bgcolor: '#0082c9',
+					bordercolor: '#0082c9',
+					font: {
+						size: 15,
+						color: 'white',
+					},
+				},
 				marker: {
 					size: results.map(r => 4 + (Math.pow(r.score, 2) * 10)),
 					opacity: results.map(r => 0.3 + (r.score * 0.7)),