Add trend-range gating, vehicle filter, sync cancel, moving time, and UI fixes

- Grey out trend ranges beyond available health history
- Reject implausibly fast (vehicle) activities on upload with feedback
- Add cancel button + cooperative cancellation for Garmin sync
- Show daily steps prominently on the dashboard
- Clear errors for malformed/empty upload ZIPs
- Snap-target dot when drawing a segment on the map
- Time-axis fallback for stationary/HIIT HR timelines; hide map when no GPS
- Parse and display moving time (timer) vs elapsed; backfill task
- Restyle SegmentsPanel like RouteLeaderboard; Laps/Routes/Segments on one row

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/pages/UploadPage.jsx

@@ -16,10 +16,17 @@ function UploadZone({ title, description, accept, endpoint, icon }) {
         if (data.status === 'SUCCESS' || data.status === 'FAILURE') {
           clearInterval(intervalsRef.current[taskId])
           delete intervalsRef.current[taskId]
+          // A successful task may still have skipped the file (e.g. a duplicate or
+          // an activity that looks like vehicle travel) — surface the reason.
+          const skipped = data.status === 'SUCCESS' && data.result?.status === 'skipped'
           setTasks(ts => ts.map(t =>
-            t.task_id === taskId ? { ...t, status: data.status === 'SUCCESS' ? 'done' : 'failed' } : t
+            t.task_id === taskId
+              ? { ...t,
+                  status: data.status === 'FAILURE' ? 'failed' : skipped ? 'skipped' : 'done',
+                  reason: skipped ? data.result?.reason : t.reason }
+              : t
           ))
-          if (data.status === 'SUCCESS') {
+          if (data.status === 'SUCCESS' && !skipped) {
             queryClient.invalidateQueries({ queryKey: ['activities'] })
             queryClient.invalidateQueries({ queryKey: ['health-summary'] })
             queryClient.invalidateQueries({ queryKey: ['health-metrics'] })
@@ -50,6 +57,10 @@ function UploadZone({ title, description, accept, endpoint, icon }) {
         pollTask(data.task_id)
       }
     },
+    onError: (err, file) => {
+      const reason = err.response?.data?.detail || 'Upload failed'
+      setTasks(t => [...t, { file: file?.name || String(file), status: 'failed', reason }])
+    },
   })
 
   const onDrop = useCallback((accepted) => {
@@ -65,6 +76,7 @@ function UploadZone({ title, description, accept, endpoint, icon }) {
   function StatusBadge({ status }) {
     if (status === 'processing') return <span className="ml-2 text-blue-400 animate-pulse">⏳ Processing</span>
     if (status === 'done') return <span className="ml-2 text-green-400">✓ Done</span>
+    if (status === 'skipped') return <span className="ml-2 text-amber-400">⚠ Skipped</span>
     if (status === 'failed') return <span className="ml-2 text-red-400">✗ Failed</span>
     return <span className="ml-2 text-green-400">✓ Queued</span>
   }
@@ -107,12 +119,19 @@ function UploadZone({ title, description, accept, endpoint, icon }) {
       {tasks.length > 0 && (
         <div className="mt-4 space-y-2">
           {tasks.map((task, i) => (
-            <div key={i} className="flex items-center justify-between text-xs bg-gray-800 rounded-lg px-3 py-2">
-              <span className="text-gray-300 truncate flex-1">{task.file}</span>
-              {task.activity_tasks !== undefined && (
-                <span className="text-gray-500 ml-2">{task.activity_tasks} activities queued</span>
+            <div key={i} className="bg-gray-800 rounded-lg px-3 py-2">
+              <div className="flex items-center justify-between text-xs">
+                <span className="text-gray-300 truncate flex-1">{task.file}</span>
+                {task.activity_tasks !== undefined && (
+                  <span className="text-gray-500 ml-2">{task.activity_tasks} activities queued</span>
+                )}
+                <StatusBadge status={task.status} />
+              </div>
+              {task.reason && (task.status === 'skipped' || task.status === 'failed') && (
+                <p className={`text-xs mt-1 ${task.status === 'skipped' ? 'text-amber-400/80' : 'text-red-400/80'}`}>
+                  {task.reason}
+                </p>
               )}
-              <StatusBadge status={task.status} />
             </div>
           ))}
         </div>