feature/VSN-2860 - add lightweight collaborator summaries endpoint for light work
Summary The existing GET /allcollaborators endpoint was slow due to fetching and mapping the full collaborator graph — including roles, addresses, work schedule, and making external HTTP calls to resolve agency and department names for every row.
Changes:
- Added findAllWithTeams() repository method using JOIN FETCH to load collaborators and their teams in a single query
- Added getAllCollaboratorSummaries() service method with a lightweight manual mapping to CollaboratorSummaryDTO
- Added GET /collaborators/summaries endpoint returning only uuid, firstName, lastName, email, and teams