I want to add a
Donate Bitcoin button to my website(s). I want to create a Bitcoin wallet with a permanent address for receiving donations. How would I do this?
Just generate a new address and put it on your website. Not sure what you mean by permanent, all addresses are permanent as long as you keep the private key safe.
Do not use a web wallet. Install Bitcoin Core or Electrum on your workstation and create a new receiving address, it will be valid permanently.
Re-using addresses is a privacy reduction but, there is no easily implemented alternative if placing a button on a web page unless you are tech savvy to setup a backend script.
Set a strong, secure password that you will never forget on your wallet to limit who can send payments. Ensure that you make a safe, secure and verified backup of your wallet and/or your wallet seed phrase and keep it up to date.