Fix: Add local: true to invitation form to prevent blank token error

[compwron]

Fixes the "Invitation token can't be blank" error that occurs when new users accept email invitations and try to set their password.

Root cause: PR #6528 refactored form_for to form_with, but form_with defaults to remote: true (AJAX submission). This causes the hidden invitation_token field to not be properly submitted with the form.

Solution: Add local: true to the form_with helper to use standard form submission instead of AJAX, ensuring the invitation_token is correctly included in the POST data.

Related to PR #6528 (form helper refactor)

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Resolves #XXXX

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