Fix project display name when resolving invite

[eleftherias]

Summary

This ensures the project display name is the one the user set during onboarding.

Similar to #3750

Change Type

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• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

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Attach screenshots if helpful.

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[coveralls]

coverage: 51.813% (-0.02%) from 51.832%
when pulling dc515db on eleftherias:resolve-invite-project-display-name
into ac1f60a on stacklok:main.