BTC node for an online store, how to set up access rights?

Question

Payment systems

A question about restricting access of unauthorized persons to the wallet file if the node is used for business.
An online store is currently being developed, which provides for payment in bitcoin.
You can pay btc directly, each time a btc address is generated for a specific product and the user pays. It also provides for the replenishment of the user's internal balance in the store, if he is registered.
What has been done:
DevOps and back-end developer set up a BTC node on a separate server. (Now you can make a test purchase, replenish the balance). The server has wallet.dat which will contain many user wallets.
Questions:
1.Where is the seed phrase of the wallet stored? Is it the same or is it different for each user's wallet?
2.How to technically close access after all the settings so that only the owner of the store has access, the owner is not a technical person and does not know how to work with the command line? How does this happen, for example, in stock exchanges? Is it possible that the admin who is working for hire has all the means?
3. How to properly resolve this issue with the staff?

Answer 1

it's bad bro
this betrays a non-professional in cue ball, i.e. misunderstanding of processes: there is NO seed and no recovery in bitcoin, there is only a pair of keys - public and private, and it is impossible to restore private from public except by brute force,
and if someone says that there is some kind of seed, this means only one thing - not only you have access to the private key, and the wallet cannot be considered only yours

Answer 2

Either yes, the person is hired, or he writes the human interface to the software
. There are no other options.