concours: contestants should be able to read server logs

[Pierre-Marie de Rodat]

Because… why not? It is not directly useful to contestants, but it could help organizers to find out what went wrong when looking at a contestant’s screen.

This is assuming that stéchec server does not leak “sensible” information, but I guess it actually has no such thing to leak.

[Alexandre Macabies]

If that's still relevant, this is a one-line fix.

[Antoine Pietri]

Fixed by 7529da5