Fix TypeScript error with unknown error type in test-scenarios route

app/api/test-scenarios/route.ts

@@ -54,10 +54,11 @@ export async function POST() {
         result: result.detection
       });
     } catch (error) {
+      const errorMessage = error instanceof Error ? error.message : String(error);
       results.push({
         scenario: scenario.name,
         input: scenario.data,
-        error: error.message
+        error: errorMessage
       });
     }
   }