is it safe to use a magnetic stand for iPad Air 5

Single or multiple small magnets in proximity of your iPad will do no harm at all; Apple’s own Magic and Folio keyboards attach by way of magnets arranged in a specific pattern. Magnets will, however, disrupt the magnetometer sensor.

Flash memory is not affected by magnetic fields. Any static magnetic field capable of causing any issues for flash storage will be so strong that your iPad will be the least of your concerns!

Unless you intend to place your iPad inside an MRI scanner or induction heating system (both of which use intense alternating magnetic fields), you needn’t have significant concern of causing lasting damage.

I would be careful.

If the magnets are too strong, they could wipe the data from your iPad's internal flash memory drive.

Strong magnetic fields in close proximity to microelectronics devices, usually does NOT fare well.l

Be aware that magnets will disrupt the iPad’s internal compass/declination sensors - but otherwise, if the stand is designed explicitly for your model of iPad, it should be “safe” to use.