Ensure element visibility works with form data. (baserow#4391)

* For element visibility to work with form data, the applicationContext must contain the element. At the moment it's missing, so when we resolve the formula, it's always null.

* Implementing Jrmi's suggestion https://github.com/baserow/baserow/pull/4391/files#r2588874445.

Author: picklepete

changelog/entries/unreleased/bug/resolved_a_bug_in_element_visibility_which_prevented_form_da.json

@@ -0,0 +1,9 @@
+{
+    "type": "bug",
+    "message": "Resolved a bug in element visibility which prevented form data from being used.",
+    "issue_origin": "github",
+    "issue_number": null,
+    "domain": "builder",
+    "bullet_points": [],
+    "created_at": "2025-12-04"
+}

web-frontend/modules/builder/components/elements/ElementPreview.vue

@@ -111,6 +111,13 @@ export default {
       getClosestSiblingElement: 'element/getClosestSiblingElement',
       loggedUser: 'userSourceUser/getUser',
     }),
+    applicationContext() {
+      return {
+        ...this.injectedApplicationContext,
+        ...this.applicationContextAdditions,
+        element: this.element,
+      }
+    },
     pageTop() {
       return this.pageTopData.value
     },

web-frontend/modules/builder/components/page/PageElement.vue

@@ -64,6 +64,13 @@ export default {
     BACKGROUND_TYPES: () => BACKGROUND_TYPES,
     CHILD_WIDTH_TYPES: () => CHILD_WIDTH_TYPES,
     WIDTH_TYPES: () => WIDTH_TYPES,
+    applicationContext() {
+      return {
+        ...this.injectedApplicationContext,
+        ...this.applicationContextAdditions,
+        element: this.element,
+      }
+    },
     themeConfigBlocks() {
       return this.$registry.getOrderedList('themeConfigBlock')
     },