The +layout.svelte auth guard only treated /login as public, so any
unauthenticated visit to /register bounced to /login?returnTo=%2Fregister.
The "Register" link on the login page therefore looped back to itself,
making the first-user-becomes-admin bootstrap path (handleRegister +
CreateUserFirstAdminRace) unreachable in production.
Extracted isPublicRoute() into web/src/lib/auth/publicRoutes.ts so the
public-route set has one source of truth and is unit-testable. Test file
explicitly comment-tags /register as a #376 regression guard.
Closes the last gap in user-mgmt umbrella #376.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
