IAV-1155 : add collaborator invitation token entities and jobTitle field
- Add UserInvitationToken entity with token (SHA-256 hashed), expiresAt, status, resendCount, lastResentAt and helper methods (isValid, markAsUsed, invalidate, incrementResend)
- Add InvitationTokenStatus enum (PENDING, USED, INVALIDATED, EXPIRED)
- Add jobTitle field to Collaborator entity
- Add invitationTokens OneToMany relation on Collaborator
Closes IAV-1155