feat(plugin-import-export): adds pluginConfig options to disable Save and Download buttons in export UI (#13158)

### What?

Adds support for two new plugin options in the import-export plugin:
- `disableSave`: disables the "Save" button in the export UI view.
- `disableDownload`: disables the "Download" button in the export UI
view.

### Why?

This allows implementers to control user access to export actions based
on context or feature requirements. For example, some use cases may want
to preview an export without saving it, or disable downloads entirely.

### How?

- Injected `disableSave` and `disableDownload` into `admin.custom` for
the `exports` collection.
- Updated the `ExportSaveButton` component to conditionally render each
button based on the injected flags.
- Defaults to `false` if the values are not explicitly set in
`pluginConfig`.

### Example

```ts
importExportPlugin({
  disableSave: true, // Defaults to false
  disableDownload: true, // Defaults to false
})

packages/plugin-import-export/src/components/ExportSaveButton/index.tsx

@@ -24,11 +24,18 @@ export const ExportSaveButton: React.FC = () => {
       routes: { api },
       serverURL,
     },
+    getEntityConfig,
   } = useConfig()
 
   const { getData, setModified } = useForm()
   const modified = useFormModified()
 
+  const exportsCollectionConfig = getEntityConfig({ collectionSlug: 'exports' })
+
+  const disableSave = exportsCollectionConfig?.admin?.custom?.disableSave === true
+
+  const disableDownload = exportsCollectionConfig?.admin?.custom?.disableDownload === true
+
   const label = t('general:save')
 
   const handleDownload = async () => {
@@ -99,10 +106,12 @@ export const ExportSaveButton: React.FC = () => {
 
   return (
     <React.Fragment>
-      <SaveButton label={label}></SaveButton>
+      {!disableSave && <SaveButton label={label} />}
+      {!disableDownload && (
         <Button disabled={!modified} onClick={handleDownload} size="medium" type="button">
           <Translation i18nKey="upload:download" t={t} />
         </Button>
+      )}
     </React.Fragment>
   )
 }

packages/plugin-import-export/src/getExportCollection.ts

@@ -34,6 +34,10 @@ export const getExportCollection = ({
           SaveButton: '@payloadcms/plugin-import-export/rsc#ExportSaveButton',
         },
       },
+      custom: {
+        disableDownload: pluginConfig.disableDownload ?? false,
+        disableSave: pluginConfig.disableSave ?? false,
+      },
       group: false,
       useAsTitle: 'name',
     },

packages/plugin-import-export/src/types.ts

@@ -15,10 +15,20 @@ export type ImportExportPluginConfig = {
    * If true, enables debug logging
    */
   debug?: boolean
+  /**
+   * If true, disables the download button in the export preview UI
+   * @default false
+   */
+  disableDownload?: boolean
   /**
    * Enable to force the export to run synchronously
    */
   disableJobsQueue?: boolean
+  /**
+   * If true, disables the save button in the export preview UI
+   * @default false
+   */
+  disableSave?: boolean
   /**
    * This function takes the default export collection configured in the plugin and allows you to override it by modifying and returning it
    * @param collection