[Refactor] Remove unused `useConfirmEmbeddedWallet` hook and clean up onboarding flow (#3632)
<!-- start pr-codex -->
## PR-Codex overview
The focus of this PR is to refactor authentication and onboarding flows, removing unused code and optimizing user creation and confirmation processes.
### Detailed summary
- Added user creation logic if user does not exist
- Removed `useConfirmEmbeddedWallet` hook
- Refactored onboarding flow and removed unused code
- Optimized handling of account confirmation and email verification
> ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your question}`
<!-- end pr-codex -->