Refactor QuillyEditor and Quill Mention Extension for Improved Functionality

- Updated `QuillyEditor.vue` to enhance the handling of model updates and internal changes, ensuring better synchronization between the editor and the model value. Introduced a new `pasteHTML` function to manage HTML content pasting more effectively.
- Refactored `quillMentionExtension.js` to improve the processing of pasted content, ensuring that only valid mentions are retained and transforming flat mention structures into nested ones for better data integrity.
- Enhanced the SCSS styles in `app.scss` to apply list styles to ordered and unordered lists within the `.field-help` class, improving the visual presentation of help text.

These changes aim to improve the overall functionality, maintainability, and user experience of the QuillyEditor component and its associated mention extension.

client/scss/app.scss

@@ -52,9 +52,17 @@ body.dark * {
 }
 
 .field-help {
-  p {
+  p, ol, ul, li {
     @apply text-gray-400 dark:text-gray-500;
   }
+
+  ol {
+    @apply list-decimal list-inside;
+  }
+
+  ul {
+    @apply list-disc list-inside;
+  }
 }
 
 .public-page {