Add public token-gated kitchen display for POS devices.

Kitchen display devices open a full-screen KDS without staff login,
with feed/stream/bump over the device token. Shared kitchen board
logic is extracted so the signed-in Kitchen page stays in sync.

config/pos.php

@@ -74,7 +74,7 @@ return [
     'device_registration_hints' => [
         'register' => 'Tracked for your team. Staff sign in on this machine — no device token is issued.',
         'customer_display' => 'Creates (or reuses) the branch customer-display token. Open the URL on a second screen facing the customer.',
-        'kitchen_display' => 'Token for kitchen screen provisioning. Kitchen currently opens the signed-in Kitchen page for this account.',
+        'kitchen_display' => 'Creates a device token. Open the kitchen URL on a wall tablet — no staff login required. Bump items from the board.',
         'receipt_printer' => 'Token for a future print agent. Paper size still comes from branch receipt settings.',
         'barcode_scanner' => 'Tracked for inventory. USB scanners work as keyboard wedges on the register today.',
         'tablet' => 'Tracked for inventory. Use Customer display or Kitchen display if the tablet should run unattended.',