Chat - Delete comment feature [S11-10]

Let users to delete their **own** comments in the discussion:
- after clicking on the comment user will see the menu options: https://zpl.io/aME30ZR

- delete comment pop-up: https://zpl.io/bJo64lx

- user's comment deleted: https://zpl.io/VDj395q

- somebody's comment deleted: https://zpl.io/2973RBw

Start by locating the discussion comment UI and the entry point that handles comment actions. Compare the existing interface with the linked designs, then verify that users can delete only their own comments, see the confirmation popup, and see the expected result after deletion.

Written by the indexing model from the issue text.