I'm Czech and while those two languages are close, "robota" is really forced work in Czech. What you called "robota" in Polish is called "práce" in Czech. In Czech, "Robota" is forced work and has bad connotations. See https://cs.wikipedia.org/wiki/Robota . It's interesting that this page doesn't have Polish translation.
A lot of Czech people use this phrase in a very subtle, almost undetectable jest, but it is still fundamentally in jest. Drawing a connection between having to work for a living and likening it to being forced to work. It's similar to saying "Back to the salt mines" meaning back to work.
I don't doubt that, you're probably from somewhere around Ostrava. There are of course regional differences. I'm from Brno and instead of "jít do práce" we usually used "jít do hokny", "jít do háčku", or just "jít makat". Whenever I hear word "robota", I connect it with my grand-grand-...-father who was forced to work ("robota") by "dráb" (overseer) and didn't like it. So he cut overseer's head with his scythe, became a village hero and founded a church there.
It is similar in Polish. “Robota” as a colloquialism is used to denote tedious, unpleasant, and labor-intensive labor (literally manual labor), and it has a coarse connotation, so it is often used in jest (“wracać do roboty” is something like “back to the salt mines”).
The typical and more genteel way to refer to work is “praca”. “Szukam pracę” is how you would typically say “I’m looking for work”, for example [0]; “ciężko pracuję” means “I work hard”. So while “robotnik” is better understood as specifically a manual laborer or someone of the working class, “pracownik” means something like “employee”.
[0] I am aware of the Czech false cognate “šukat” :).
Interesting that in Ukrainian робота and праця are synonymous. Although, some derived words are different in meaning. Like робітник is a worker but працівник is an employee. I see in another comment that the same is true in Polish.
