feat: add POS register screen with full-screen touch-optimized layout

Standalone register at /pos bypassing the admin sidebar layout:
- Two-panel layout: product search/grid (60%) + cart/payment (40%)
- Product search with barcode scan support (UPC lookup on Enter)
- Custom item entry dialog for ad-hoc items
- Cart with line items, tax, totals, and remove-item support
- Payment dialogs: cash (quick amounts + change calc), card, check
- Drawer open/close with balance reconciliation and over/short
- Auto-creates pending transaction on first item added
- POS link added to admin sidebar nav (module-gated)
- Zustand store for POS session state, React Query for server data

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

packages/admin/src/components/pos/pos-top-bar.tsx

@@ -0,0 +1,91 @@
+import { Link, useRouter } from '@tanstack/react-router'
+import { useAuthStore } from '@/stores/auth.store'
+import { usePOSStore } from '@/stores/pos.store'
+import { Button } from '@/components/ui/button'
+import { Badge } from '@/components/ui/badge'
+import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select'
+import { ArrowLeft, LogOut, DollarSign } from 'lucide-react'
+import type { DrawerSession } from '@/api/pos'
+import { useState } from 'react'
+import { POSDrawerDialog } from './pos-drawer-dialog'
+
+interface POSTopBarProps {
+  locations: { id: string; name: string }[]
+  locationId: string | null
+  onLocationChange: (id: string) => void
+  drawer: DrawerSession | null
+}
+
+export function POSTopBar({ locations, locationId, onLocationChange, drawer }: POSTopBarProps) {
+  const router = useRouter()
+  const user = useAuthStore((s) => s.user)
+  const logout = useAuthStore((s) => s.logout)
+  const [drawerDialogOpen, setDrawerDialogOpen] = useState(false)
+
+  const drawerOpen = drawer?.status === 'open'
+
+  function handleLogout() {
+    logout()
+    router.navigate({ to: '/login', replace: true })
+  }
+
+  return (
+    <>
+      <div className="h-12 border-b border-border bg-card flex items-center justify-between px-3 shrink-0">
+        {/* Left: back + location */}
+        <div className="flex items-center gap-3">
+          <Link to="/" className="flex items-center gap-1 text-sm text-muted-foreground hover:text-foreground">
+            <ArrowLeft className="h-4 w-4" />
+            <span className="hidden sm:inline">Admin</span>
+          </Link>
+
+          {locations.length > 1 ? (
+            <Select value={locationId ?? ''} onValueChange={onLocationChange}>
+              <SelectTrigger className="h-8 w-48 text-sm">
+                <SelectValue placeholder="Select location" />
+              </SelectTrigger>
+              <SelectContent>
+                {locations.map((loc) => (
+                  <SelectItem key={loc.id} value={loc.id}>{loc.name}</SelectItem>
+                ))}
+              </SelectContent>
+            </Select>
+          ) : locations.length === 1 ? (
+            <span className="text-sm font-medium">{locations[0].name}</span>
+          ) : null}
+        </div>
+
+        {/* Center: drawer status */}
+        <Button
+          variant="ghost"
+          size="sm"
+          className="flex items-center gap-2"
+          onClick={() => setDrawerDialogOpen(true)}
+        >
+          <DollarSign className="h-4 w-4" />
+          {drawerOpen ? (
+            <Badge variant="default" className="text-xs">
+              Drawer Open &mdash; ${parseFloat(drawer!.openingBalance).toFixed(2)}
+            </Badge>
+          ) : (
+            <Badge variant="outline" className="text-xs">Drawer Closed</Badge>
+          )}
+        </Button>
+
+        {/* Right: user + logout */}
+        <div className="flex items-center gap-2">
+          <span className="text-sm text-muted-foreground">{user?.firstName}</span>
+          <Button variant="ghost" size="icon" className="h-8 w-8" onClick={handleLogout} title="Sign out">
+            <LogOut className="h-4 w-4" />
+          </Button>
+        </div>
+      </div>
+
+      <POSDrawerDialog
+        open={drawerDialogOpen}
+        onOpenChange={setDrawerDialogOpen}
+        drawer={drawer}
+      />
+    </>
+  )
+}