Optimize bulk deletion flow and handle UI residuals

- Check for existing delete button before initiating deletion.
- Remove lingering delete button from DOM if present.
- Ensure sequential deletion of selected conversations.

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "ChatGPT Bulk Delete",
-  "version": "2.8",
+  "version": "2.9",
   "description": "A Chrome extension to bulk delete ChatGPT conversations",
   "icons": {
     "48": "icon48.png"