Batch 1: dashboard, maps, segments rewrite, health, sync UX

Fixes:
- Dashboard: featured most-recent activity card with map + stats
- Maps default to Street; preferCanvas + larger tile buffer for smoother pan/zoom
- Running cadence as colour-banded dots + 165 spm guide line
- Routes: inline row expansion, rename (PATCH /routes/{id}), podium + deltas, tiled map
- Records: remove reversed pace Y-axis
- Profile: remove resting HR; add goal weight
- Health: snapshot weight carry-forward; VO2 trend axis 30-70;
  weight goal line + kg/st-lb toggle + axis max; sleep 8h/avg lines
- Garmin sync progress moved to global store with persistent floating bar

Features:
- Speed-coloured activity route (default) with Speed/Solid toggle
- GPS-geometry segments: draw on map, match across all activities,
  1st/2nd/3rd leaderboard + podium badges (replaces old distance segments)
- Lap bests: best time per lap across a route + delta column
- Body Battery: highlight activity time windows

Schema: users.goal_weight_kg ALTER; new segments/segment_efforts tables.
Removes RouteSegment, the Segments page, and segment-bests endpoints.

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

frontend/src/components/activity/SegmentsPanel.jsx

@@ -0,0 +1,78 @@
+import { useState } from 'react'
+import { useQuery, useQueryClient } from '@tanstack/react-query'
+import api from '../../utils/api'
+import { formatDuration, formatDistance } from '../../utils/format'
+
+const MEDALS = { 1: '🥇', 2: '🥈', 3: '🥉' }
+
+function Leaderboard({ segmentId }) {
+  const { data } = useQuery({
+    queryKey: ['segment', segmentId],
+    queryFn: () => api.get(`/segments/${segmentId}`).then(r => r.data),
+  })
+  if (!data) return <p className="text-xs text-gray-600 py-2">Loading…</p>
+  if (!data.leaderboard?.length) return <p className="text-xs text-gray-600 py-2">No efforts yet — still matching.</p>
+  return (
+    <div className="space-y-0.5 py-1">
+      {data.leaderboard.map((e, i) => (
+        <div key={e.activity_id} className="flex items-center gap-2 text-xs">
+          <span className="w-5 text-right">{MEDALS[e.rank] || i + 1}</span>
+          <span className="font-mono text-gray-200 w-14 text-right">{formatDuration(e.duration_s)}</span>
+          <a href={`/activities/${e.activity_id}`} className="text-gray-400 hover:text-blue-400 truncate flex-1">{e.activity_name}</a>
+        </div>
+      ))}
+    </div>
+  )
+}
+
+export default function SegmentsPanel({ segments }) {
+  const qc = useQueryClient()
+  const [open, setOpen] = useState(null)
+
+  const remove = async (id) => {
+    if (!confirm('Delete this segment?')) return
+    await api.delete(`/segments/${id}`)
+    qc.invalidateQueries()
+  }
+
+  return (
+    <div className="space-y-1">
+      <div className="flex items-center gap-3 pb-1.5 border-b border-gray-800 text-xs text-gray-600 uppercase tracking-wide">
+        <span className="flex-1">Segment</span>
+        <span className="w-14 text-right">This run</span>
+        <span className="w-14 text-right">Best</span>
+        <span className="w-10 text-right">Place</span>
+      </div>
+      {segments.map(seg => {
+        const isPodium = seg.rank && seg.rank <= 3
+        const delta = seg.best_s != null ? seg.duration_s - seg.best_s : null
+        return (
+          <div key={seg.segment_id} className="border-b border-gray-800/40">
+            <div className="flex items-center gap-3 py-1.5 text-sm">
+              <button onClick={() => setOpen(open === seg.segment_id ? null : seg.segment_id)}
+                className="flex-1 text-left text-gray-300 text-xs truncate hover:text-white">
+                {seg.name}
+                <span className="text-gray-600 ml-2">{formatDistance(seg.distance_m)}</span>
+              </button>
+              <span className={`font-mono text-xs w-14 text-right ${isPodium ? 'text-yellow-400 font-semibold' : 'text-gray-200'}`}>
+                {formatDuration(seg.duration_s)}
+              </span>
+              <span className="font-mono text-xs w-14 text-right text-gray-500">
+                {seg.best_s != null ? formatDuration(seg.best_s) : '--'}
+              </span>
+              <span className="w-10 text-right text-xs">
+                {isPodium
+                  ? <span title="New podium time on this activity">{MEDALS[seg.rank]}</span>
+                  : delta != null
+                    ? <span className="text-red-400 font-mono">+{formatDuration(delta)}</span>
+                    : <span className="text-gray-700">--</span>}
+              </span>
+              <button onClick={() => remove(seg.segment_id)} className="text-gray-700 hover:text-red-400 text-xs" title="Delete segment">✕</button>
+            </div>
+            {open === seg.segment_id && <Leaderboard segmentId={seg.segment_id} />}
+          </div>
+        )
+      })}
+    </div>
+  )
+}