Add • to cells without computed departure time in the times stops table

### Description and goal

https://www.sketch.com/s/44a4dfe4-6ef5-4f9f-92d3-72b79136e5da/p/40BF39F6-06B6-4BF3-9616-20FDE6FCE8C3/canvas

<img width="852" height="329" alt="Image" src="https://github.com/user-attachments/assets/026c22b6-1b11-4449-b877-464fe899c3dc" />

### Acceptance criteria

A dot should be visible on every cells that don't have computed departure time