Airtag bike holder with M3 bolts

I have made some optimizations to the original design, such as adding chamfers and fillets, while removing some unnecessary elements. It has been changed to an M3 bolt assembly, and you will need to use M3 embedded nuts and countersunk bolts. The original bottom part has been altered to a semi-hollow design, making the airtag less noticeable, and a drainage hole has been reserved.