Fan mega issue

@JaredC01 has a nice [2U 2x80mm fan bracket](https://github.com/JaredC01/LabStack/blob/main/10in%20Rack/STLs/2U%202x%2080mm%20Fan%20Panel.stl)

But what about:
- 1U multi fan bracket
- top/bottom mount bracket for larger fans (1-4x 120mm, 1-9x 80mm)
- side mount bracket

Maybe in conjunction with filtering #27?

Also think about the concept of airflow thru the case and "hot-side" vs "cold-side" like they do with 19" racks in data centers. Natural convection is also good, bottom-to-top airflow is probably the way to go unless you are otherwise constrained. (although maybe the contents of the rack might inhibit? hmm maybe the other shelf designs needs to have air holes?)

Start by reviewing the linked 2U 2x80mm fan bracket STL and issue #27. Clarify which bracket variants and airflow constraints are in scope, then define completion as the requested fan-mount designs being specified and their corresponding STL files provided.

Written by the indexing model from the issue text.