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/pt.json

@@ -1101,6 +1101,11 @@
   "TomTom roads first; OpenStreetMap fills the rest, simulated": "Primeiro as vias do TomTom; o OpenStreetMap completa o resto com fluxo simulado",
   "TomTom roads first; OpenStreetMap fills the rest, simulated (needs a TomTom key)": "Primeiro as vias do TomTom; o OpenStreetMap completa o resto com fluxo simulado (precisa de uma chave do TomTom)",
   "Hybrid": "Híbrido",
+  "Lines": "Linhas",
+  "Dots": "Pontos",
+  "Road lines colored by live flow: green to red": "Vias coloridas pelo fluxo ao vivo: do verde ao vermelho",
+  "Moving dots colored by live flow": "Pontos em movimento coloridos pelo fluxo ao vivo",
+  "Moving dots": "Pontos em movimento",
   "TomTom key unavailable": "Chave do TomTom indisponível",
   "TomTom daily budget reached": "Limite diário do TomTom atingido",
   "Monthly traffic allowance used": "Cota mensal de trânsito esgotada",