I too had a darkroom in a bathroom, maybe thirty five years ago. There were a couple of not too commonly done things that made it workable.
The first was light-proofing the window, a low horizontal window hinged at the top that opened outwards. Just inside the casing there was a small "step" that surrounded the window that allowed me to snugly fit a removable panel to darken the room.
Just in front of the "step", at the top, there was a small metal slotted plate that was, I think, designed to allow a screen to latch. I used it to help hold the panel in place. Into that plate went a small metal bit I fitted into an "arm" I constructed with fittings for two safelights.
The arm was maybe two feet long, and by it's weight, levered against the panel to keep it tight. It was a very clean installlation. There were no pieces affixed to the building and everything was removable with no screw holes etc. The panel fitted very tightly and let almost no light in so I could work in daytime.
I built a rolling stand for the enlarger. Actually, built it into the baseboard frame of the enlarger, a 45 MC series, so they became a unit, and the space under the enlarger became rolling storage. Likewise a small sink was made as a rolling unit.
Both rolling units went elsewhere when not in photographic use.
Washing without a dedicated print washer was by fill and dump washing. I don't remember where I first read that Kodak specified for washing by continuous flow, a certain number of complete changes of water, but I took that to heart and applied the concept to fill and dump. I filled a small plastic tub and agitated the prints in it for something like a minute, dumped it completely and refilled. Then, repeat, repeat , repeat... If I recall, Kodak specified something like ten(?) complete changes of water, but someone here will know for sure. It was in one or another pamphlet. There was a test using a dye to see how completely the water got changed.
It worked like a charm. I have never really trusted any washer that doesn't do complete dumps, so this system felt like a safe and reliable way to wash prints.