deps: react-leaflet 1.8 -> 4.2 (+ leaflet 1.9) — the last legacy react-* lib

Ground-up hooks rewrite of the app's core map. Removes the final batch of
React-19-blocking warnings (legacy context on Map/LayersControl/TileLayer/
Marker/CircleMarker/Circle/Tooltip + ReactDOM.render from the old controls).

Core: <Map> -> <MapContainer>; .leafletElement refs (6 files) -> the map/
layer instances directly, via a <MapReady> child (useMap) + plain refs on
Marker/Circle/GeoJSON; controlled viewport (onViewportChanged + state.center/
zoom) -> <MapEvents> (useMapEvents moveend/zoomend) + imperative setView;
onClick -> eventHandlers={{click}}; Path styling -> pathOptions/style;
subsUnion takes the L.Map directly.

The 4 v1-only plugins reimplemented (new in-repo helpers under Maps/):
- react-leaflet-control -> MapControl (L.Control + createPortal)
- react-leaflet-google  -> GoogleMutantLayer (createLayerComponent +
  leaflet.gridlayer.googlemutant; Google Maps API already loaded by Gkeys)
- react-leaflet-fullscreen -> createControlComponent + leaflet.fullscreen
- leaflet-sleep / leaflet-graphicscale kept as vanilla (work on leaflet 1.9)

Browser-verified: /fires (tiles, OSM+Google layer switch, custom control,
fullscreen, graphic scale, pan/zoom -> re-fetch, no NaN), fire detail
(GeoJSON rect + fitBounds), home (3 maps coexist; SelectionMap draggable
marker -> updatePosition + distance circle). Console now shows 0 React
warnings on home/fires. REST smoke byte-identical.

PENDIENTE.md

@@ -18,7 +18,7 @@ desarrollo (no en producción) y **bloquean el salto a React 19**. Estado:
 | react-bootstrap | 0.31 → 2 | ✅ hecho (CSS sigue en Bootstrap 4) |
 | reactstrap + 3 deps muertas | — | ✅ eliminadas (0 usos) |
 | react-router-dom | 4.2 → 6.30 | ✅ hecho (history 5, HOC `withRouterCompat`) |
-| **react-leaflet + leaflet** | 1.8/1.3 → 4/1.9 | ⏸️ **diferida** (mapa = feature central; 4 plugins v1-only sin equivalente v4; ver UPGRADE.md) |
+| react-leaflet + leaflet | 1.8/1.3 → 4.2/1.9 | ✅ hecho (Map→MapContainer, refs directas, useMap/useMapEvents; 4 plugins reimplementados: MapControl portal, GoogleMutantLayer, fullscreen, sleep/graphicscale vanilla; ver UPGRADE.md) |
 | **Bootstrap CSS/JS** | 4.1 → 5 | ⏸️ **diferida** (carrusel/navbar jQuery BS4; ver UPGRADE.md) |
 
 Lo verificado en navegador tras cada lib: `/`, `/fires`, `/fire/archive/<hex>`,
@@ -28,9 +28,10 @@ parámetros por defecto; `UNSAFE_componentWillReceiveProps` (FromNow, FireStats,
 Fires, SelectionMap) → `getDerivedStateFromProps`/`componentDidUpdate`; Reconnect
 (banner Blaze `meteorStatus` con `findDOMNode`) → React nativo con
 `useTracker(Meteor.status)`; react-share 2→5 y react-progress-bar.js → progressbar.js
-(ambos tiraban `findDOMNode`/`defaultProps`). **Tras esto, la ÚNICA fuente de
-warnings en consola es react-leaflet + sus 4 plugins (diferida).** (Queda un
-`findDOMNode` menor solo en `/status`: el `<Blaze serverFacts>` de Status.js, página admin.)
+(ambos tiraban `findDOMNode`/`defaultProps`); y react-leaflet 1.8→4.2 (mapa central,
+4 plugins reimplementados). **Tras esto la consola tiene 0 warnings de React en las
+rutas principales** (verificado forzando re-render en / y /fires). Único resto para
+React 19: el `<Blaze serverFacts>` de Status.js (`findDOMNode`), solo en `/status` (admin).
 
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