Pin/Unpin UI Controls for Staff

[Mr-Weather]

Estimated time: 1 hour
Estimated complexity (T-shirt size): S
Dependencies: Must have made pin/unpin features and ensured it's staff-only
Description:

1. Add a Pin/Unpin control to the topic UI
2. Display control only to authorized staff.
3. Update UI state immediately after pin/unpin actions.

Acceptance criteria:

1. Staff users see pin/unpin controls; students do not.
2. Pin/unpin updates are reflected immediately after pin/unpin actions without a page refresh.