Mobile app migration from /webrest to /api

[tommaso-ascani]

This work is required to migrate the mobile app integration from cti-server to nethcti-middleware without breaking existing login flows.

Scope

1. update ctiapp-authproxy API paths from /webrest/... to /api/...;
2. switch auth flow from legacy token to JWT (/api/login + Bearer token);
3. align QR-code flow between nethvoice-cti (QR generation) and ctiapp-authproxy (QR handling), since current QR payloads may still contain legacy non-JWT tokens.