Ender 5 Power Relocation

This print allows you to move the stock power switch and power cable receptacle onto the back-left of the frame.

I designed this because I completely removed the electronics box from my Ender-5 (all of the PCBs are just sitting on standoffs now), but I didn't want the power receptacle and switch just casually flopping around with 120VAC going through them.

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#### Update: 2024/04/28
(been a while yes I know, life had been life-ing)

Fusion360:
- Redesigned the part in Fusion360, because FreeCAD was too buggy and the parameterization in Fusion360 makes designing significantly more maintainable)
- Removed the FreeCAD file, because it was having compute errors and was no longer accurate
- `power-box-v3-main.stl` is the original (non-updated) design from FreeCAD
- Added a lid (finally)

Box:
- The box should largely be the same, save for some of the fillets; I copied the dimensions from FreeCAD exactly
- Removed the rails that slot into the 4020 rails, as they