Closes#14789
### What problem does this PR solve?
User API endpoints (`login`, `user_profile`, `user_add`,
`forget_reset_password`) were returning full user objects via
`to_json()` / `to_dict()`, which included sensitive fields like
`password` and `access_token` in the response body. This leaks
credentials to the client.
This PR adds a `to_safe_dict()` method on the `User` model that strips
sensitive fields (`password`, `access_token`) and replaces all affected
call sites to use it.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve?
- Moved if not all([email, new_pwd, new_pwd2]) guard to the top, before
any decryption that could crash on None value
- Removed the redundant REDIS_CONN.get() call — one call is sufficient
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] Refactoring
