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/tiles.js

@@ -133,6 +133,23 @@ function renderSidebarSupport(supportServices) {
   var hr = document.createElement("hr");
   hr.className = "sidebar-divider";
   $sidebarSupport.appendChild(hr);
+
+  // ── Restart Entire System button (bottom, visually separated)
+  var restartDivider = document.createElement("hr");
+  restartDivider.className = "sidebar-divider";
+  $sidebarSupport.appendChild(restartDivider);
+
+  var restartBtn = document.createElement("button");
+  restartBtn.className = "sidebar-support-btn sidebar-restart-btn";
+  restartBtn.id = "sidebar-btn-restart";
+  restartBtn.innerHTML =
+    '<span class="sidebar-support-icon sidebar-restart-icon" aria-hidden="true">\u21BB</span>' +
+    '<span class="sidebar-support-text">' +
+      '<span class="sidebar-support-title">Restart Entire System</span>' +
+      '<span class="sidebar-support-hint sidebar-restart-hint">Restarts the computer, desktop, and all services</span>' +
+    '</span>';
+  restartBtn.addEventListener("click", function() { openRestartConfirmDialog(); });
+  $sidebarSupport.appendChild(restartBtn);
 }
 
 function buildTile(svc) {