feat: POS PIN unlock with employee number + PIN auth

- Add employeeNumber and pinHash fields to users table
- POST /auth/pin-login: takes combined code (4-digit employee# + 4-digit PIN)
- POST /auth/set-pin: employee sets their own PIN (requires full auth)
- DELETE /auth/pin: remove PIN
- Lock screen with numpad, auto-submits on 8 digits, visual dot separator
- POS uses its own auth token separate from admin session
- Admin "POS" link clears admin session before navigating
- /pos route has no auth guard — lock screen is the auth
- API client uses POS token when available, admin token otherwise
- Auto-lock timer reads pos_lock_timeout from app_config (default 15 min)
- Lock button in POS top bar, shows current cashier name

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shared/src/schemas/index.ts

@@ -1,8 +1,8 @@
 export { PaginationSchema } from './pagination.schema.js'
 export type { PaginationInput, PaginatedResponse } from './pagination.schema.js'
 
-export { UserRole, RegisterSchema, LoginSchema } from './auth.schema.js'
-export type { RegisterInput, LoginInput } from './auth.schema.js'
+export { UserRole, RegisterSchema, LoginSchema, PinLoginSchema, SetPinSchema } from './auth.schema.js'
+export type { RegisterInput, LoginInput, PinLoginInput, SetPinInput } from './auth.schema.js'
 
 export {
   BillingMode,