Restructure the core API module to improve clarity, consistency, and
maintainability:
- Introduce `defineApiRoutes()` helper for declarative route definitions
with built-in config validation at startup
- Add `apiSuccess()` / `apiError()` response utilities; enforce their
use across all handlers (core and modules)
- Move auth enforcement to route definitions (`auth: 'public' | 'user' |
'admin'`), removing manual auth checks from handlers
- Extract core routes into `core-routes.js`; router now has no knowledge
of specific features
- Rename `nx-route.js` to `route-handler.js` and update package.json
export accordingly
- Update ARCHITECTURE.md to reflect new API conventions and point to
`src/core/api/README.md` for details
Move the "Publier le package" section from DEV.md to a new
PUBLICATION.md file, and add references to ARCHITECTURE.md and
PUBLICATION.md in the main DEV.md index. This reduces the size of
DEV.md and improves discoverability by grouping related content
into focused documents.