Keep the progress bar on one line, and portal modals out of the top bar (0.42.1)

The stacks-list bar sat below the name and grew the row when an action
started. It now runs inline to the right of the name and service count,
filling the space before the CPU column, so the row keeps its height.
Label, percentage and byte detail sit on that same line.

Also fixes the self-update prompt being cut off at the top. The top bar
is backdrop-blurred, and a non-none backdrop-filter makes an element the
containing block for `position: fixed` descendants — so the dialog
centred itself in the 60px header instead of the viewport and overflowed
off-screen. ConfirmDialog and the update overlay now render through a
portal on document.body. ConfirmDialog also scrolls itself rather than
its backdrop, which would otherwise strand its top edge.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016pMmFFkdfxkoYjcEcpZTa5

frontend/package.json

@@ -1,7 +1,7 @@
 {
   "name": "stackpilot-frontend",
   "private": true,
-  "version": "0.42.0",
+  "version": "0.42.1",
   "type": "module",
   "scripts": {
     "dev": "vite",