The easiest way to do that is to change all the structures to use 0 logistics or tactical slots, since you may not be able to give the planets "Infinite" slots (a really big number like 999999 would work though). Please read some of the stickies here if you do not know how to even edit files.
That said, I do not recommend you actually do this, because it will likely cause the AI problems, since they tend to do things like max out their defenses at the homeworld. If they can never reach a maximum point, they'll be building defenses forever and may not invest much in a fleet.
