In all honestly, I wouldn't trust it as a daily commuter.
There's a high chance that it will be fine, but there is still a chance for it to fail. Especially if you decide, for any reason, to be fully loaded.
Also, we don't know how much you weigh, or how much stuff you will be travelling with.
In theory, the frame could be absolutely fine, but with use, there's a chance that the dent has exposed the frame to the elements and more likely to fail over time with corrosion etc..
Another thing to look out for is whether the bike is stolen, that dent looks similar to what would happen if someone yanked it from it's lock, and if it was a cheap lock then it could break.
The bike is cheap though, and if it were me, I'd buy it just for the parts! Try and source a replacement frame and swap all bits over. But again, I don't know how mechanically inclined you are.