Attachments in shared notes are deleted after adding a category

Bug Description
When a shared note is categorized by the recipient (without changing ownership), all attachments (e.g., images, videos) within the note are deleted from the server. This issue occurs specifically when the shared user modifies the note's category.

Steps to reproduce
User A creates a note with attachments (e.g., images, videos) in the Notes app.
User A shares the note with User B.
User B changes the category of the shared note (e.g., assigns it to "Work" or "Personal").
Check the note content after the category change.

Expected behaviour
The note and its attachments (images, videos, etc.) should remain intact when the recipient changes the category of a shared note.

Actual behaviour
Attachments within the note are deleted from the server, and the note no longer displays them. A "Failed to load" error appears for the missing attachments.

No file or test is named. Start by reproducing the category change with a shared note containing attachments, then trace the shared-note category update and attachment persistence or deletion path. Done means changing the recipient's category preserves all attachments and they no longer produce a "Failed to load" error.