fix: use direct VAADIN path for push script URL (#22827)

The correct approach is to use the direct VAADIN/... path without any
navigation prefix. This works because the <base href> already points
to the servlet root, so relative URLs resolve correctly to
{context-path}/{servlet-path}/VAADIN/...

Fixes #22826

Author: Artur-

flow-server/src/main/java/com/vaadin/flow/server/BootstrapHandler.java

@@ -1509,18 +1509,18 @@ protected static String getPushScript(BootstrapContext context) {
         VaadinRequest request = context.getRequest();
         // Parameter appended to JS to bypass caches after version upgrade.
         String versionQueryParam = "?v=" + Version.getBuildHash();
-        // Load client-side dependencies for push support
-        String pushJSPath = BootstrapHandlerHelper.getServiceUrl(request) + "/";
 
+        String pushJs;
         if (request.getService().getDeploymentConfiguration()
                 .isProductionMode()) {
-            pushJSPath += ApplicationConstants.VAADIN_PUSH_JS;
+            pushJs = ApplicationConstants.VAADIN_PUSH_JS;
         } else {
-            pushJSPath += ApplicationConstants.VAADIN_PUSH_DEBUG_JS;
+            pushJs = ApplicationConstants.VAADIN_PUSH_DEBUG_JS;
         }
 
-        pushJSPath += versionQueryParam;
-        return pushJSPath;
+        // Use direct path - the <base href> already points to the servlet root,
+        // so VAADIN/... resolves correctly to {context}/{servlet}/VAADIN/...
+        return pushJs + versionQueryParam;
     }
 
     protected static void setupErrorDialogs(Element style) {

flow-server/src/main/java/com/vaadin/flow/server/communication/IndexHtmlRequestHandler.java

@@ -445,9 +445,9 @@ private void addDevTools(Document indexDocument,
 
         indexDocument.body().appendChild(new Element("vaadin-dev-tools"));
 
-        String pushUrl = BootstrapHandlerHelper.getServiceUrl(request) + "/"
-                + ApplicationConstants.VAADIN_PUSH_DEBUG_JS;
-        addScriptSrc(indexDocument, pushUrl);
+        // Use direct path - the <base href> already points to the servlet root,
+        // so VAADIN/... resolves correctly to {context}/{servlet}/VAADIN/...
+        addScriptSrc(indexDocument, ApplicationConstants.VAADIN_PUSH_DEBUG_JS);
     }
 
     static boolean isAllowedDevToolsHost(AbstractConfiguration configuration,

flow-server/src/test/java/com/vaadin/flow/server/communication/JavaScriptBootstrapHandlerTest.java

@@ -170,7 +170,7 @@ public void should_respondPushScript_when_enabledInDeploymentConfiguration()
 
         // Using regex, because version depends on the build
         Assert.assertTrue(json.get("pushScript").asString().matches(
-                "^\\./VAADIN/static/push/vaadinPush\\.js\\?v=[\\w\\.\\-]+$"));
+                "^VAADIN/static/push/vaadinPush\\.js\\?v=[\\w\\.\\-]+$"));
     }
 
     @Test
@@ -188,7 +188,7 @@ public void should_respondPushScript_when_nonRootServletPath()
 
         // Using regex, because version depends on the build
         Assert.assertTrue(json.get("pushScript").asString().matches(
-                "^\\./VAADIN/static/push/vaadinPush\\.js\\?v=[\\w\\.\\-]+$"));
+                "^VAADIN/static/push/vaadinPush\\.js\\?v=[\\w\\.\\-]+$"));
     }
 
     @Test
@@ -223,7 +223,7 @@ public void should_respondPushScript_when_annotatedInAppShell()
 
         // Using regex, because version depends on the build
         Assert.assertTrue(json.get("pushScript").asString().matches(
-                "^\\./VAADIN/static/push/vaadinPush\\.js\\?v=[\\w\\.\\-]+$"));
+                "^VAADIN/static/push/vaadinPush\\.js\\?v=[\\w\\.\\-]+$"));
     }
 
     @Test