How are the mechanical locks for windows and doors planned? Should standard locks and things like that be installed, or is a high-quality burglar protection already being built in?
If standard parts are installed that any burglar apprentice can open in no time on the second day, an alarm system is not very useful either, since it usually only reports that someone unauthorized has broken in. Depending on the system.
With high-quality mechanical protection, an alarm system may not be necessary.
First of all, it should be ensured that burglars ideally don't manage to open windows or doors in the first place.
If not already done, go to the police advisory office and get advice there.
I would rather invest the money for an alarm system initially in mechanical protective devices. And only possibly retrofit an alarm system later. Although empty conduits for this can already be laid during house construction.