Users can share a View with another user

Expected behavior:

- a saved user view will have a dedicated URL
- sharing that URL with another user will allow the target user to see that view of the data
- the target user can choose to:
- copy/duplicate that view (creates a new view that belongs to the target user)
- save that view (lists that view in their dropdown but any changes made by the original user will also change it for the target user)

Notes:

- option 1: query params
- option 2: backend support

The issue names no files, tests, or entry points. Start by locating saved user view persistence, URL handling, and the view dropdown, then determine how sharing, copying, and saving should work across users. Done means a saved view has a shareable URL and the recipient can view, duplicate, or save it as described.

Written by the indexing model from the issue text.