Upgraded jquery to 4.0.0

webpack.config.js

@@ -119,7 +119,14 @@ Encore
     // requires WebpackEncoreBundle 1.4 or higher
     .enableIntegrityHashes(Encore.isProduction())
 
-    // uncomment if you're having problems with a jQuery plugin
+    // Force all jquery imports to the UMD build so webpack always receives the
+    // jQuery function directly instead of an ESM namespace object. Without this,
+    // webpack's ESM interop wraps jquery.module.js in a namespace
+    // { default, jQuery, $ } which has no .fn, crashing Bootstrap's
+    // defineJQueryPlugin when it tries to access $.fn.alert.
+    .addAliases({
+        'jquery': path.resolve(__dirname, 'node_modules/jquery/dist/jquery.js')
+    })
     .autoProvidejQuery()