fix: Modal in the context menu disappears unless hovered (#10333)

# Pull Request Template

## Description

This PR resolves the issue where the modal in the context menu
disappears when not being hovered over.

**Cause of issue.**
The problem occurred because the modal-related component was placed
inside `MessageContextMenu.vue`, and the parent wrapper was using the
classes `group-hover:visible invisible`. This caused the modal to only
appear when the message item, where the context menu was opened, was
hovered over.

**Solution**
To fix this, I removed the `group-hover:visible` invisible class from
the parent wrapper and moved it into the `woot-button` within the
`MessageContextMenu.vue` component. Additionally, I added a nested group
with the class group/context-menu, allowing the focus to remain on the
context menu itself.

Fixes
https://linear.app/chatwoot/issue/PR-1415/modal-in-the-context-menu-disappears-unless-hovered

## Type of change

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

## How Has This Been Tested?

**Loom video**

**Before**

https://www.loom.com/share/458f90708664493c86e909a56869d065?sid=0564a508-09a5-4e73-800b-8042140a22ba

**After**

https://www.loom.com/share/c119936d181d406d89468f9482ef6b81?sid=5cf3b1b4-6c66-4f8c-8f93-a62465a93b57

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] 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/modules/conversations/components/MessageContextMenu.vue

@@ -187,6 +187,7 @@ export default {
       color-scheme="secondary"
       variant="clear"
       size="small"
+      class="invisible group-hover/context-menu:visible"
       @click="handleOpen"
     />
     <ContextMenu