Fix: Trim whitespace from email before processing

[stella-entry]

Resolves #6689

Summary

• Added &.strip to email parameter in update_user_email method to remove leading/trailing whitespace
• Added test case to verify whitespace is stripped from email input

Problem

When users accidentally include leading or trailing spaces in their email address while updating their profile, the system would attempt to process the email with whitespace intact, resulting in errors.

Solution

Strip whitespace from the email parameter before processing, similar to standard email input sanitization practices.

Testing

• Added new test case strips whitespace from email in spec/requests/users_spec.rb
• All existing tests continue to pass

How to Test

1. Sign in as a volunteer
2. Go to profile edit page
3. Enter email with leading/trailing spaces: test@example.com
4. Submit the form
5. Email should be saved as test@example.com (without spaces)