Update import button to show "Uploading…" state during file upload (#9365)

* Update import button to show 'Uploading…' state during file upload

- Update DropToImport component to show 'Uploading…' text and disable button during import
- Update Notion ImportDialog to show 'Uploading…' text during submission
- Improves user feedback during import operations

* Move ellipsis character out of translated strings

- Separate ellipsis from 'Uploading' translation to improve i18n
- Use string concatenation: t('Uploading') + '…' instead of t('Uploading…')

---------

Co-authored-by: codegen-sh[bot] <131295404+codegen-sh[bot]@users.noreply.github.com>

plugins/notion/client/components/ImportDialog.tsx

@@ -70,7 +70,7 @@ export function ImportDialog({ integrationId, onSubmit }: Props) {
       </div>
       <Flex justify="flex-end">
         <Button onClick={handleStartImport} disabled={submitting}>
-          {t("Start import")}
+          {submitting ? t("Uploading") + "…" : t("Start import")}
         </Button>
       </Flex>
     </Flex>