1.8.1

release: v1.8.1 - "open folder" button on received files

After a file lands, render a small "Mở thư mục" button next to the
completed entry that opens the OS file explorer with the saved file
pre-selected. Saves the user a trip through Settings → Downloads to
locate what they just received.

- connection.ts: thread the saved path through updateFileProgress on
  completion, plus into the audit log details.
- session.ts: new renderFileRowActions helper, idempotent so menu
  re-renders don't double up. Wired into both the regular file list
  and the host-mode mini panel.
- session.css: action button styling matched to existing chip design.