Implement users, roles, and equipment API

feat(backend): add reusable role authorization helpers

API contracts have been defined for schemas, operations, and role-based access rights.

API contracts have been defined for schemas, operations, and role-based access rights.

merge: integrate yana/backend/api contracts

refactor(backend): regroup photo and estimate endpoints

feat(backend): add secure defect photo storage API

refactor(backend): regroup photo and estimate endpoints

feat(backend): add secure defect photo storage API

merge: integrate yana/backend/api contracts

merge: integrate yana/backend/api contracts

feat(mvp): add end-to-end estimate pipeline with mock AI

feat(mvp): add end-to-end estimate pipeline with mock AI

merge: integrate repair request API

style(docs): remove trailing whitespace

feat(backend): implement repair request management API

feat(backend): implement repair request management API

merge: integrate backend/json contracts

add card-3

feat(docs): add integration contracts and examples for ML Service

add card-3

feat(docs): add integration contracts and examples for ML Service