Build the Review Queue chart's actual trace from per-second samples, not lap averages

A lap can span many minutes, so plotting one flat value per lap hid real
within-lap variation -- a single-lap hill repeat rendered as a dead-flat
line despite the pace/HR swinging throughout it. The actual pace/HR trace
now comes from activity_samples (per-second telemetry) when available,
looking up each sample's enclosing lap only for the target band/phase
color. Falls back to the previous lap-stepped rendering when an activity
has no samples.

frontend/src/pages/ReviewQueue.tsx

@@ -132,7 +132,7 @@ export function ReviewQueue() {
                   </p>
                 )}
 
-                <ExpectedVsActualChart laps={item.laps} />
+                <ExpectedVsActualChart laps={item.laps} samples={item.samples} />
 
                 <div className="review-item-actions">
                   {manuallyAssignableKinds.map((k) => (