fix favicon

sqlpage/sqlpage/internal/theme.sql

@@ -4,6 +4,6 @@ SELECT 'shell' AS component
 , $title AS title
 , lower($title)||'.sql' AS link
 , 'favicon.svg' AS image
-, 'favicon.ico' AS favicon
+, 'favicon.png' AS favicon
 , 'manifest.json' AS manifest
 ;