feat(admin): implement management UI and CRUD APIs for all entities

Add full CRUD operations for Pokemon, Habitats, Items, Recipes, and Configs
Switch package manager from npm to pnpm across the project
Remove static seed data in favor of UI-driven data management

frontend/src/App.vue

@@ -2,7 +2,8 @@
 const navItems = [
   { label: 'Pokemon', to: '/pokemon' },
   { label: '栖息地', to: '/habitats' },
-  { label: '物品 / 材料单', to: '/items' }
+  { label: '物品 / 材料单', to: '/items' },
+  { label: '管理', to: '/admin' }
 ];
 </script>