New API endpoints:
- POST /api/auth/cli/device-code/new — issue device code + user code
- GET /api/auth/cli/device-code/[code] — poll device code status
- POST /api/auth/cli/device-code/[code]/approve — approve by device code
- POST /api/auth/cli/device-code/approve-by-user-code — approve by user code
Updated cli-auth page to auto-approve on page load after authentication
(no manual "Approve" button click needed).
Enables `claudemesh login` and `claudemesh register` CLI commands.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>