Fix track coloring hover: inline reactive vars so Svelte tracks deps

statColorMode() hid hasSpeedTrack etc. from Svelte's compiler so the
{#each} block never re-rendered when timeseries loaded. Inline the
ternary directly so all reactive variables are visible to the tracker.

site/src/components/ActivityDetail.svelte

@@ -407,7 +407,12 @@
   <!-- Stats panel -->
   <div class="grid grid-cols-2 lg:grid-cols-1 gap-px bg-zinc-800 rounded-xl overflow-hidden">
     {#each stats as s}
-      {@const cm = statColorMode(s.key)}
+      {@const cm =
+        s.key === 'speed'      && hasSpeedTrack   ? 'speed'     :
+        s.key === 'heart_rate' && hasHrTrack      ? 'hr'        :
+        s.key === 'power'      && hasPowerTrack   ? 'power'     :
+        s.key === 'elevation'  && hasElevTrack    ? 'elevation' :
+        s.key === 'cadence'    && hasCadenceTrack ? 'cadence'   : null}
       <div
         class="bg-zinc-900 px-4 py-3 transition-colors"
         class:hover:bg-zinc-800={cm !== null}