fix(progress): rework transfer progress panel (#424)

Migrate the transfer progress UI to tuirealm 4, where the stdlib
`ProgressBar` widget was dropped, by rebuilding the dual-bar panel on
top of `Gauge`.

- Restore the unified two-bar look: the full bar (top) and partial bar
  (bottom) draw joined borders so they read as a single panel; a single
  file shows one fully-bordered bar.
- Redraw on every file boundary in the send/recv queue loops so the
  full bar's (N/total) counter advances even for small files that finish
  within one in-loop redraw interval.
- Track progress with a single `TransferProgress` (exact file count from
  the pre-scan, lazy partial/full computation) and consolidate the theme
  progress-bar fields.

src/ui/activities/filetransfer.rs

@@ -70,7 +70,8 @@ enum Id {
     MkdirPopup,
     NewfilePopup,
     OpenWithPopup,
-    TransferProgressBar,
+    TransferProgressBarFull,
+    TransferProgressBarPartial,
     QuitPopup,
     RenamePopup,
     ReplacePopup,