Add unit tests for SettingsForm

[devin-ai-integration]

Summary

Adds a new TestSettingsForm test class to provide unit test coverage for the SettingsForm in realworld/accounts/forms.py. The form previously had no test coverage.

The test class includes 8 tests covering:

• Valid form submission
• Optional password field behavior
• Password hashing when a new password is provided
• Password preservation when no password is provided
• Email format validation
• Save method correctly updating all user fields
• commit=False behavior in save method
• Empty bio and image fields being allowed

Review & Testing Checklist for Human

• Verify test isolation: tests use setUpTestData which shares the user instance across tests. Confirm that tests modifying the user (like test_password_update_hashes_password) don't affect other tests due to transaction rollback
• Run the full test suite locally to confirm all 21 accounts tests pass: python manage.py test realworld.accounts
• Consider if any additional edge cases should be tested (e.g., duplicate email validation, required field validation for name)

Notes

• Tests follow the existing patterns in the test file (class-level form_data, setUpTestData, etc.)
• All tests passed locally before PR creation

Link to Devin run: https://app.devin.ai/sessions/b35b3dabc503408daa6a9624449617e9
Requested by: Jude Partovi (@jpartovi)

[devin-ai-integration]

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