feat: Allow removing labels via conversation context menu (#13525)

# Pull Request Template

## Description

This PR adds support for removing labels from the conversation card
context menu. Assigned labels now show a checkmark, and clicking an
already-selected label will remove it.

Fixes
https://linear.app/chatwoot/issue/CW-6400/allow-removing-labels-directly-from-the-right-click-menu
https://github.com/chatwoot/chatwoot/issues/13367
## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

**Screencast**


https://github.com/user-attachments/assets/4e3a6080-a67d-4851-9d10-d8dbf3ceeb04




## 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/ConversationItem.vue

@@ -10,6 +10,7 @@ export default {
     'assignAgent',
     'assignTeam',
     'assignLabels',
+    'removeLabels',
     'updateConversationStatus',
     'toggleContextMenu',
     'markAsUnread',
@@ -63,6 +64,7 @@ export default {
     @assign-agent="assignAgent"
     @assign-team="assignTeam"
     @assign-label="assignLabels"
+    @remove-label="removeLabels"
     @update-conversation-status="updateConversationStatus"
     @context-menu-toggle="toggleContextMenu"
     @mark-as-unread="markAsUnread"