fix: calculer ETA depuis horizons API — évite dépendance aux données stale en base

frontend/src/components/SpotPanel/SpotPanel.jsx

@@ -12,6 +12,17 @@ const TREND_CONFIG = {
   decreasing: { icon: '📉', label: 'Amélioration en cours',    cls: 'trend--good' },
 };
 
+const ETA_BUFFER_KM = 5;
+
+function computeEta(score, horizons) {
+  if (score?.distance != null && score.distance < ETA_BUFFER_KM) return 0;
+  for (const h of [6, 12, 24, 48]) {
+    const horizon = horizons?.[`h${h}`];
+    if (horizon?.distanceKm != null && horizon.distanceKm < ETA_BUFFER_KM) return h;
+  }
+  return null;
+}
+
 function etaLabel(etaHours) {
   if (etaHours === 0)  return { icon: '🚨', label: 'Impact en cours',           cls: 'eta--now'  };
   if (etaHours === 6)  return { icon: '⚠️',  label: 'Impact prévu dans ~6h',     cls: 'eta--soon' };
@@ -82,7 +93,7 @@ export default function SpotPanel({ spot, activeStep, onClose }) {
             : (
               <>
                 {activeStep === 'now' && (() => {
-                  const eta = etaLabel(displayScore.etaHours ?? undefined);
+                  const eta = etaLabel(computeEta(data?.score, data?.horizons));
                   return (
                     <div className={`spot-panel__eta ${eta.cls}`}>
                       <span className="spot-panel__eta-icon">{eta.icon}</span>