add mapbox gl option, gps location, journey reorder + polish

- Mapbox GL provider alongside Leaflet for trip and journey maps (opt-in in
  settings with token, style presets incl. 3D on satellite, quality mode,
  experimental badge).
- GPS "blue dot" with heading cone on mobile; three-state FAB (off / show /
  follow), geodesic accuracy circle, desktop-hidden since browser IP geo is
  too coarse for navigation.
- Marker drift fix: outer wrap no longer carries inline position/transform,
  so mapbox's translate keeps the pin pinned at every zoom and pitch.
- Journey map popup (mapbox-gl): Apple-Maps-style tooltip on marker
  highlight/click showing entry title + location / date subline.
- Journey feed reorder: up/down controls to the left of each entry reorder
  sort_order within a day. Server endpoint, optimistic store update, rollback
  on failure.
- Journey entry editor: desktop modal now centers over the feed column only,
  backdrop still blurs the whole page (map included).
- Scroll-sync guard on journey: marker click locks the sync so smooth-scroll
  can't steer the highlight to a neighbouring entry mid-animation.
- Misc: map top-padding aligned with hero, live/synced badges replaced by a
  compact back-button in the hero, skeleton entries no longer pollute the
  journey map, journey detail no longer shows map on mobile path when
  combined view is active.

client/src/components/Map/LocationButton.tsx

@@ -0,0 +1,56 @@
+import { Navigation, LocateFixed, Locate } from 'lucide-react'
+import type { TrackingMode } from '../../hooks/useGeolocation'
+
+interface Props {
+  mode: TrackingMode
+  error: string | null
+  onClick: () => void
+  // Offset from the bottom edge — callers push this up above the mobile
+  // bottom nav. Defaults to 20px for desktop.
+  bottomOffset?: number
+}
+
+// Three-state FAB. Matches the Apple/Google Maps pattern:
+//   off    → outline locate icon
+//   show   → filled locate (blue dot is visible on the map)
+//   follow → filled navigation arrow (map follows + rotates with heading)
+export default function LocationButton({ mode, error, onClick, bottomOffset = 20 }: Props) {
+  const Icon = mode === 'follow' ? Navigation : mode === 'show' ? LocateFixed : Locate
+  const isActive = mode !== 'off'
+  const title = error
+    ? error
+    : mode === 'off'
+      ? 'Show my location'
+      : mode === 'show'
+        ? 'Follow my location'
+        : 'Stop following'
+
+  return (
+    <button
+      type="button"
+      onClick={onClick}
+      title={title}
+      aria-label={title}
+      style={{
+        position: 'absolute',
+        bottom: bottomOffset,
+        right: 12,
+        zIndex: 1000,
+        width: 42,
+        height: 42,
+        borderRadius: '50%',
+        border: 'none',
+        cursor: 'pointer',
+        background: isActive ? '#3b82f6' : 'var(--bg-card, white)',
+        color: isActive ? 'white' : (error ? '#ef4444' : 'var(--text-muted, #6b7280)'),
+        boxShadow: '0 2px 10px rgba(0,0,0,0.25)',
+        display: 'flex',
+        alignItems: 'center',
+        justifyContent: 'center',
+        transition: 'background 0.2s, color 0.2s',
+      }}
+    >
+      <Icon size={20} strokeWidth={mode === 'follow' ? 2.5 : 2} />
+    </button>
+  )
+}