feat: show accumulated distance per gear item in gear tab

Compute total distance from allActivities where gear name matches and
display it inline next to each gear item. Also add gear field to
ActivitySummary type so index shard gear data is accessible in the UI.

site/src/components/AthleteView.svelte

@@ -151,6 +151,13 @@
 
   $: if (activeTab === 'gear' && isOwner && !gearFetched && !gearLoading) gearFetch();
 
+  $: gearDistances = Object.fromEntries(
+    gearItems.map(g => [
+      g.name,
+      allActivities.filter(a => a.gear === g.name).reduce((sum, a) => sum + (a.distance_m ?? 0), 0),
+    ])
+  );
+
   $: if (activeTab === 'segments' && segmentsHandle && !segmentsFetched && !segmentsLoading) {
     segmentsLoading = true;
     segmentsFetched = true;
@@ -483,6 +490,9 @@
                 <div class="px-4 py-3 border-b border-zinc-800 flex items-center gap-3 last:border-0">
                   <span class="text-lg leading-none">{GEAR_ICONS[item.type] ?? '⚙️'}</span>
                   <span class="flex-1 text-sm text-white" class:text-zinc-500={item.retired}>{item.name}</span>
+                  {#if gearDistances[item.name] > 0}
+                    <span class="text-xs text-zinc-400">{formatDistance(gearDistances[item.name])}</span>
+                  {/if}
                   {#if item.retired}
                     <span class="text-xs text-zinc-600 border border-zinc-700 rounded px-1.5 py-0.5">Retired</span>
                   {/if}

site/src/lib/types.ts

@@ -69,6 +69,7 @@ export interface ActivitySummary {
   climbing_vam_mh?: number | null;
   climbing_time_s?: number | null;
   source: string | null;
+  gear: string | null;
   privacy: Privacy;
   detail_url: string | null;
   track_url: string | null;