QUA: Create finished plan popup only for the user running the plan

Currently, the finished plan popup shows up for all users logged in. This is not a problem for single-user setups, but can cause some frustration when using remote access with multiple users. In such cases, the popup can interrupt the other user's work, while not necessarily being an interesting event for them.

Start by tracing how plan completion triggers the finished-plan popup and how the current user is identified in the frontend. Confirm the behavior with multiple logged-in users using remote access, then verify that only the user who ran the plan sees the popup while other users can continue working.

Written by the indexing model from the issue text.