feat(traffic): Lines and Dots toggles; hosts choose which road modes they offer

createTrafficSource({ roadModes }) lets a host offer a subset of the TomTom,
OSM and Hybrid road modes (all three by default). Without OSM the layer never
draws simulated roads, and a single mode shows no road chip.

While flow is live the Street Traffic row offers Lines (every road with flow
as a steady green/amber/red line, from the heat-line renderer) and Dots (the
moving dots), saved in layer state and share links. Defaults: Lines off,
Dots on.

src/i18n/locales/es.json

@@ -2699,6 +2699,11 @@
   "Zoom in for vector tile coverage": "Acércate para cargar las teselas vectoriales",
   "Camera coverage unavailable": "Cobertura de cámaras no disponible",
   "Hybrid": "Híbrido",
+  "Lines": "Líneas",
+  "Dots": "Puntos",
+  "Road lines colored by live flow: green to red": "Líneas de vías coloreadas por el flujo en vivo: de verde a rojo",
+  "Moving dots colored by live flow": "Puntos en movimiento coloreados por el flujo en vivo",
+  "Moving dots": "Puntos en movimiento",
   "TomTom roads only, each with its live flow": "Solo vías de TomTom, cada una con su flujo en vivo",
   "TomTom roads only, each with its live flow (needs a TomTom key)": "Solo vías de TomTom, cada una con su flujo en vivo (necesita una clave de TomTom)",
   "OpenStreetMap roads, with TomTom flow matched when available": "Vías de OpenStreetMap, con el flujo de TomTom emparejado cuando está disponible",