feat(checkout): searchable address fields and Rajaongkir integration

Admin SPA:
- Changed billing/shipping state from Select to SearchableSelect

Customer SPA:
- Added cmdk package for command palette
- Created popover, command, and searchable-select UI components
- Added searchable country and state fields to checkout
- Fetches countries/states from /countries API
- Auto-clears state when country changes

Backend:
- Added generic woonoow/shipping/before_calculate hook
- Removed hardcoded Rajaongkir session handling

Documentation:
- Updated RAJAONGKIR_INTEGRATION.md with:
  - Complete searchable destination selector plugin code
  - JavaScript implementation
  - React component version
  - REST API endpoint for destination search

customer-spa/package.json

@@ -27,6 +27,7 @@
         "@tanstack/react-query": "^5.90.5",
         "class-variance-authority": "^0.7.1",
         "clsx": "^2.1.1",
+        "cmdk": "^1.1.1",
         "lucide-react": "^0.547.0",
         "react": "^18.3.1",
         "react-dom": "^18.3.1",