fix: Variable search item not showing after braces/commas (#11864)

# Pull Request Template

## Description

This PR fixes an issue where typing variables, like `{{contact.name}}`,
caused the variable list to miss showing `contact.name`. The search key
in this case became `contact.name}},` which didn't match any available
options. The logic in `VariableList.vue` only checked the part after the
last comma and didn’t fully sanitize the input.

**Solution**
Updated `searchKey` to remove all {} and commas for accurate matching.

Fixes
[CW-4574](https://linear.app/chatwoot/issue/CW-4574/i-dont-see-an-option-for-contactname-it-shows-initially-but-it-doesnt)

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

### Loom video

https://www.loom.com/share/fc86e53853ad49e6acf6de57ebbd8fcb?sid=6702f896-d1a3-4c5a-9eb7-b96b5ed91531


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

app/javascript/dashboard/components/widgets/conversation/VariableList.vue

@@ -1,6 +1,7 @@
 <script>
 import { mapGetters } from 'vuex';
 import { MESSAGE_VARIABLES } from 'shared/constants/messages';
+import { sanitizeVariableSearchKey } from 'dashboard/helper/commons';
 import MentionBox from '../mentions/MentionBox.vue';
 
 export default {
@@ -16,6 +17,9 @@ export default {
     ...mapGetters({
       customAttributes: 'attributes/getAttributes',
     }),
+    sanitizedSearchKey() {
+      return sanitizeVariableSearchKey(this.searchKey);
+    },
     items() {
       return [
         ...this.standardAttributeVariables,
@@ -25,8 +29,8 @@ export default {
     standardAttributeVariables() {
       return MESSAGE_VARIABLES.filter(variable => {
         return (
-          variable.label.includes(this.searchKey) ||
-          variable.key.includes(this.searchKey)
+          variable.label.includes(this.sanitizedSearchKey) ||
+          variable.key.includes(this.sanitizedSearchKey)
         );
       }).map(variable => ({
         label: variable.key,