[User/Commenting] Add Field Validation, Auth Guards and Replies Tree

[andrxpie]

Description

Final polish to the comments feature: adding client-side field validation, checking permissions, and displaying nested replies in a compact format within the Drawer.

Scope of Work

• Add character limits on the client side (max. 500 characters + change this on the backend) and display a counter.
• Add user authorization checks (if a guest, block the TextArea or display a button).
• Implement a tree-like display of replies: due to the limited space in the Drawer, create a small indent (16px) for the second level of nesting. For deep replies, use the @name format in the text instead of endless indents.
• Implement a “Reply” button that activates the input field under a specific comment.

Acceptance Criteria

• Empty comments are not submitted; the character counter works in real time.
• Only authorized users see the input fields and action buttons (edit/delete).
• Replies are clearly structured and grouped under parent comments in the Drawer interface.