fix(admin,admin-ui): copy public folder as part of admin build (#5057)

**What**
- Copies `/public` folder into Admin build
- Updates the version of `dotenv` to match the version used in other Medusa dependencies. This will prevent errors when trying to link the `admin` package into a local repository for testing.

packages/admin-ui/src/node/webpack/get-webpack-config.ts

@@ -1,4 +1,5 @@
 import ReactRefreshPlugin from "@pmmmwh/react-refresh-webpack-plugin"
+import CopyPlugin from "copy-webpack-plugin"
 import HtmlWebpackPlugin from "html-webpack-plugin"
 import MiniCssExtractPlugin from "mini-css-extract-plugin"
 import path from "node:path"
@@ -177,6 +178,15 @@ export function getWebpackConfig({
 
       new webpack.DefinePlugin(envVars),
 
+      new CopyPlugin({
+        patterns: [
+          {
+            from: path.resolve(__dirname, "..", "ui", "public"),
+            to: path.resolve(dest, "public"),
+          },
+        ],
+      }),
+
       !isProd && new ReactRefreshPlugin(),
 
       ...webpackPlugins,