feat: add cash in/out UI and hide drawer balance from cashier

- Cash In / Cash Out buttons in drawer dialog when open
- Amount + reason form, adjustment history with IN/OUT badges
- Drawer badge shows "Drawer Open" without balance (manager info only)
- API helpers for addAdjustment and getAdjustments

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

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

@@ -64,9 +64,7 @@ export function POSTopBar({ locations, locationId, onLocationChange, drawer }: P
         >
           <DollarSign className="h-4 w-4" />
           {drawerOpen ? (
-            <Badge variant="default" className="text-xs">
-              Drawer Open &mdash; ${parseFloat(drawer!.openingBalance).toFixed(2)}
-            </Badge>
+            <Badge variant="default" className="text-xs">Drawer Open</Badge>
           ) : (
             <Badge variant="outline" className="text-xs">Drawer Closed</Badge>
           )}