Hole to trace clearance determination
DIN 7985 Phillips pan-head screws have a head diameter of 6.0mm maximum. It will be different if you use a socket-head cap screw or other shape of head, of course.
Standard fit hole size is 3.3mm, so you need to allow for 3.15mm (3mm radius + (3.3-3)/2) off the nominal center of the hole. If you use a larger hole (eg. 3.6mm) you'll need to allow more like 3.3mm.
Add the clearance you need for the voltages etc., probably no less than 0.5mm, so more like 4mm radius.
Also you should keep fragile components away from the mounting hole in case the assembly person slips with the screwdriver.