fix: restore WeatherAverageBar component in session header and adjust styling

Reintroduced the WeatherAverageBar component in the WeatherSessionPage to display team averages. Updated the styling of the WeatherAverageBar for improved spacing. Enhanced the EvolutionIndicator component to use dynamic background colors for better visibility of status indicators.

src/components/weather/WeatherCard.tsx

@@ -48,12 +48,45 @@ function EvolutionIndicator({
   if (direction === null) return null;
 
   if (direction === 'up') {
-    return <span className="inline-flex items-center justify-center w-5 h-5 rounded-full bg-green-100 text-green-700 text-xs font-bold shrink-0" title="Amélioration">↑</span>;
+    return (
+      <span
+        className="inline-flex items-center justify-center w-5 h-5 rounded-full text-xs font-bold shrink-0"
+        style={{
+          backgroundColor: 'color-mix(in srgb, var(--success) 18%, transparent)',
+          color: 'var(--success)',
+        }}
+        title="Amélioration"
+      >
+        ↑
+      </span>
+    );
   }
   if (direction === 'down') {
-    return <span className="inline-flex items-center justify-center w-5 h-5 rounded-full bg-red-100 text-red-700 text-xs font-bold shrink-0" title="Dégradation">↓</span>;
+    return (
+      <span
+        className="inline-flex items-center justify-center w-5 h-5 rounded-full text-xs font-bold shrink-0"
+        style={{
+          backgroundColor: 'color-mix(in srgb, var(--destructive) 18%, transparent)',
+          color: 'var(--destructive)',
+        }}
+        title="Dégradation"
+      >
+        ↓
+      </span>
+    );
   }
-  return <span className="inline-flex items-center justify-center w-5 h-5 rounded-full bg-muted/30 text-muted text-xs font-bold shrink-0" title="Stable">→</span>;
+  return (
+    <span
+      className="inline-flex items-center justify-center w-5 h-5 rounded-full text-xs font-bold shrink-0"
+      style={{
+        backgroundColor: 'color-mix(in srgb, var(--muted) 15%, transparent)',
+        color: 'var(--muted)',
+      }}
+      title="Stable"
+    >
+      →
+    </span>
+  );
 }
 
 export function WeatherCard({ sessionId, currentUserId, entry, canEdit, previousEntry }: WeatherCardProps) {