you could either:
Remove WebUI\Password_SHA1 from your config temporarily so you can log in without a password and set it again
Get another clean qBittorent (Dektop, new container), generate a Password with it and copy WebUI\Password_PBKDF2 from its config. Not sure if you need to remove WebUI\Password_SHA1.
Hash you password like qBittorrent does and insert it into your config