Large Aluminium foil bakingpan

I don't see why not. (In general, aluminum foil can be reused in a lot of contexts, unless it's damaged in some way that makes it unusable. Or perhaps if it's dirty and can't be cleaned.)

With a pre-made aluminum foil pan, you can probably rinse it if it gets a bit dirty. One problem with these pre-made pans is that they often have a lot of little "wrinkles" that capture food and make them difficult to clean. But with hard biscuit-type baking, this isn't really a food safety issue, and simply rinsing/scrubbing gently/brushing may be enough to get an old batch's remnants off.

Eventually with a few reuses these pans may develop small holes. Again, that's more of an issue with liquid materials that could leak through them than with biscotti. But eventually they will wear out.