DEV - Account Creation Bug

[lyannne]

Description (Similar to #146)
When a user registers for a new account, even if registration is successful, a notification incorrectly states that there was an error. However, the user is able to log in with those credentials, confirming the account was created.

When trying to register with an email/username that already exists, the system returns a generic "Internal Server Error" message. While it correctly blocks duplicate accounts, the message is not user-friendly and should clearly explain that the account already exists.

Steps to Reproduce

• Go to the registration page.
• Enter valid new user credentials → observe error message, but account still works.
• Try to register again with the same credentials → observe "Internal Server Error."

Acceptance Criteria

• Successful registration shows success message (no error).
• Duplicate account attempts return a clear, user-friendly notification.
• Other registration errors (e.g., invalid password format) are also displayed in plain language.
• No generic "Internal Server Error" messages should be shown to users.
• Tested with new and existing accounts.