fix(files): show legacy file warning banner for trusted-access users

Trusted-access users (Pres Mgmt admins) were getting file_list_status='ready'
when selecting .ppt/.doc/.xls files, so the prominent warning banner never
rendered — only the small per-row warning in the file table was visible.

- element_input_files_tbl: introduce 'warn_legacy' status for trusted users;
  show a yellow warning banner (vs red blocked banner for non-trusted users)
- ae_comp__event_files_upload: change button disabled check from != 'ready'
  to === 'blocked_legacy' so 'warn_legacy' does not accidentally block upload

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/events/ae_comp__event_files_upload.svelte

@@ -279,7 +279,7 @@ async function handle_input_upload_files({
             transition-all
             "
         disabled={$events_sess.files.disable_submit__event_file_obj ||
-            $events_sess.files.status__file_list != 'ready'}>
+            $events_sess.files.status__file_list === 'blocked_legacy'}>
         {#await ae_promises.upload__hosted_file_obj}
             <LoaderCircle class="m-1 animate-spin" />
             <span class="">