Fix upload auto-refresh, health data refresh, and HR zone recalculation

- UploadPage now polls task status every 2s and invalidates activity,
  health-summary, and health-metrics queries on completion so new
  activities and health data appear without a hard refresh
- Garmin and Strava export endpoints now return a task_id for polling
- Updating max HR in Profile triggers a background Celery task to
  recalculate hr_zones for all existing activities; profile page shows
  a confirmation note when this is queued
- Add CLAUDE.md with repo architecture and dev commands

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/UploadPage.jsx

@@ -1,10 +1,38 @@
-import { useState, useCallback } from 'react'
+import { useState, useCallback, useEffect, useRef } from 'react'
 import { useDropzone } from 'react-dropzone'
-import { useMutation } from '@tanstack/react-query'
+import { useMutation, useQueryClient } from '@tanstack/react-query'
 import api from '../utils/api'
 
 function UploadZone({ title, description, accept, endpoint, icon }) {
   const [tasks, setTasks] = useState([])
+  const queryClient = useQueryClient()
+  const intervalsRef = useRef({})
+
+  const pollTask = useCallback((taskId) => {
+    if (intervalsRef.current[taskId]) return
+    const intervalId = setInterval(async () => {
+      try {
+        const { data } = await api.get(`/upload/task/${taskId}`)
+        if (data.status === 'SUCCESS' || data.status === 'FAILURE') {
+          clearInterval(intervalsRef.current[taskId])
+          delete intervalsRef.current[taskId]
+          setTasks(ts => ts.map(t =>
+            t.task_id === taskId ? { ...t, status: data.status === 'SUCCESS' ? 'done' : 'failed' } : t
+          ))
+          if (data.status === 'SUCCESS') {
+            queryClient.invalidateQueries({ queryKey: ['activities'] })
+            queryClient.invalidateQueries({ queryKey: ['health-summary'] })
+            queryClient.invalidateQueries({ queryKey: ['health-metrics'] })
+          }
+        }
+      } catch { /* ignore transient poll errors */ }
+    }, 2000)
+    intervalsRef.current[taskId] = intervalId
+  }, [queryClient])
+
+  useEffect(() => {
+    return () => { Object.values(intervalsRef.current).forEach(clearInterval) }
+  }, [])
 
   const upload = useMutation({
     mutationFn: async (file) => {
@@ -16,7 +44,11 @@ function UploadZone({ title, description, accept, endpoint, icon }) {
       return { file: file.name, ...data }
     },
     onSuccess: (data) => {
-      setTasks(t => [...t, { ...data, status: 'queued' }])
+      const task = { ...data, status: data.task_id ? 'processing' : 'queued' }
+      setTasks(t => [...t, task])
+      if (data.task_id) {
+        pollTask(data.task_id)
+      }
     },
   })
 
@@ -30,6 +62,13 @@ function UploadZone({ title, description, accept, endpoint, icon }) {
     multiple: true,
   })
 
+  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 === 'failed') return <span className="ml-2 text-red-400">✗ Failed</span>
+    return <span className="ml-2 text-green-400">✓ Queued</span>
+  }
+
   return (
     <div className="bg-gray-900 rounded-xl border border-gray-800 p-5">
       <div className="flex items-center gap-3 mb-3">
@@ -73,7 +112,7 @@ function UploadZone({ title, description, accept, endpoint, icon }) {
               {task.activity_tasks !== undefined && (
                 <span className="text-gray-500 ml-2">{task.activity_tasks} activities queued</span>
               )}
-              <span className="ml-2 text-green-400">✓ Queued</span>
+              <StatusBadge status={task.status} />
             </div>
           ))}
         </div>