As follow up of #2636, we should aim to align floordiv behavior across backends whenever possible. ### Updates 1. Currently work in progress in [fix/align-div-by-zero](https://github.com/narwhals-dev/narwhals/tree/fix/align-div-by-zero) branch. 2. pandas is gonna be fun, especially for typing π€― 3. After all, this is not too bad for pandas-like case (https://github.com/narwhals-dev/narwhals/commit/3552f9169570777261e58a43252db6e4e8657e40), but this is the best I could do in typing (https://github.com/narwhals-dev/narwhals/commit/fd759b3e0fc8fc06bc3b48df66e1fcba23850ca2) 4. I am close to having it ready, I would like to add a few more test cases, including the _right_ (`__rfloordiv__` and `__rtruediv__`) version of the ops