Fix: Replace deprecated @import with @use directive for bootstrap

Replace the deprecated Sass @import directive with the modern @use directive
to resolve ESLint compilation errors during webpack build process.

Author: phavekes

assets/scss/application.scss

@@ -1,7 +1,7 @@
 @charset "utf-8";
 
 @use "vars";
-@import "~bootstrap";
+@use "bootstrap";
 
 .nav-header {
   padding-bottom: 9px;