feat: implement consistent restart UX across Sovran_SystemsOS Hub

- Add Restart Entire System sidebar action with amber treatment and divider
- Add shared restart confirmation dialog with conflict detection
- Update reboot overlay: new title, body copy, status progression, error card
- Improve doReboot(): failure handling, aria-live status messages
- Standardize 'restart required' / 'Restart Entire System' terminology
- Update security.js reboot flow to use shared doReboot()
- Update installer.py button label
- Add .btn-restart-amber, .restart-conflict-box, .sidebar-restart-btn CSS

app/sovran_systemsos_web/static/js/rebuild.js

@@ -69,7 +69,7 @@ function onRebuildDone(result) {
     // Auto-reload the page after a short delay so tiles and toggles reflect the new state
     setTimeout(function() { window.location.reload(); }, 1200);
   } else if (result === "reboot_required") {
-    if ($rebuildStatus) $rebuildStatus.textContent = "✓ Done — reboot required";
+    if ($rebuildStatus) $rebuildStatus.textContent = "✓ Done — restart required";
     if ($rebuildReboot) $rebuildReboot.style.display = "inline-flex";
   } else {
     if ($rebuildStatus) $rebuildStatus.textContent = "✗ Something went wrong";