fix: status 200 + bandeau avertissement données périmées

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/Map/SargassesMap.css

@@ -31,6 +31,22 @@
   z-index: 10;
 }
 
+/* ── Avertissement données périmées ── */
+.smap-stale {
+  position: absolute;
+  bottom: max(52px, calc(52px + env(safe-area-inset-bottom)));
+  left: max(10px, calc(10px + env(safe-area-inset-left)));
+  background: rgba(251, 191, 36, 0.92);
+  backdrop-filter: blur(4px);
+  border-radius: 6px;
+  padding: 4px 10px;
+  font-size: 11px;
+  color: #78350f;
+  font-weight: 600;
+  pointer-events: none;
+  z-index: 10;
+}
+
 /* NavigationControl MapLibre — remonte au-dessus de la barre Android */
 .maplibregl-ctrl-bottom-right {
   bottom: env(safe-area-inset-bottom) !important;

frontend/src/components/Map/SargassesMap.jsx

@@ -189,6 +189,7 @@ export default function SargassesMap({ onSpotSelect, selectedSpotId, activeStep,
   const [layerOpacity, setLayerOpacity] = useState(1);
   const [mapStyle,     setMapStyle]     = useState(null);   // null = style not yet ready
   const [dataDate,     setDataDate]     = useState(null);
+  const [dataStale,    setDataStale]    = useState(false);  // true = données > 6h
 
   const tilesOrigin = window.location.origin;
 
@@ -199,8 +200,9 @@ export default function SargassesMap({ onSpotSelect, selectedSpotId, activeStep,
         if (s.lastObservation?.detectedAt) {
           setDataDate(new Date(s.lastObservation.detectedAt));
         }
+        setDataStale(!s.healthy);
       })
-      .catch(() => {});
+      .catch(() => setDataStale(true));
   }, []);
 
   // Load cartoon map style once — map is only mounted when style is ready,
@@ -283,6 +285,12 @@ export default function SargassesMap({ onSpotSelect, selectedSpotId, activeStep,
         </div>
       )}
 
+      {dataStale && (
+        <div className="smap-stale">
+          Satellite en attente — données possiblement périmées
+        </div>
+      )}
+
       {activeStep === 'now' && (
         <Source
           id="observations"