feat: redesign shipment request cart as inventory-integrated flow

Replace the wizard-style 4-step shipment cart with an inventory-page-
integrated flow matching the legacy portal UX. Users now add items
directly from inventory detail rows via "+" buttons, with a persistent
cart bar showing status. The "Complete Release" page is a flat form
instead of a multi-step wizard.

Key changes:
- Add ShipmentCartProvider context for cross-page cart state
- Add CartBar component (start/cancel release, view status)
- Integrate cart column into inventory detail table with per-row
  add buttons, plant mismatch indicators, and "Add All" support
- Rewrite /shipment-requests/new as flat Complete Release page
- Add check_only param to cart API (avoid auto-creating on mount)
- Add server-side plant constraint validation on cart items
- Add batch add API endpoint for "Add All" functionality
- Delete deprecated wizard cart and inventory browser dialog

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -21,7 +21,7 @@
     "@hookform/resolvers": "^3.9.1",
     "@prisma/client": "^6.1.0",
     "@radix-ui/react-accordion": "^1.2.2",
-    "@radix-ui/react-alert-dialog": "^1.1.4",
+    "@radix-ui/react-alert-dialog": "^1.1.15",
     "@radix-ui/react-avatar": "^1.1.2",
     "@radix-ui/react-checkbox": "^1.1.3",
     "@radix-ui/react-dialog": "^1.1.15",