add PWA installable + recalibrer scoring échelle Guadeloupe

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

backend/src/Controller/SpotScoreController.php

@@ -312,8 +312,8 @@ class SpotScoreController extends AbstractController
     private function scoreToLevel(int $score): string
     {
         return match (true) {
-            $score <= 30 => 'low',
-            $score <= 70 => 'medium',
+            $score <= 15 => 'low',
+            $score <= 55 => 'medium',
             default      => 'high',
         };
     }