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/state.js

@@ -49,6 +49,9 @@ const $btnSave        = document.getElementById("btn-save-report");
 const $btnCloseModal  = document.getElementById("btn-close-modal");
 
 const $rebootOverlay  = document.getElementById("reboot-overlay");
+const $rebootMainCard = document.getElementById("reboot-main-card");
+const $rebootErrorCard = document.getElementById("reboot-error-card");
+const $rebootSubmessage = document.getElementById("reboot-submessage");
 
 const $credsModal     = document.getElementById("creds-modal");
 const $credsTitle     = document.getElementById("creds-modal-title");
@@ -101,5 +104,11 @@ const $upgradeConfirmBtn  = document.getElementById("upgrade-confirm-btn");
 const $upgradeCancelBtn   = document.getElementById("upgrade-cancel-btn");
 const $upgradeCloseBtn    = document.getElementById("upgrade-close-btn");
 
+// Restart confirm dialog
+const $restartConfirmModal  = document.getElementById("restart-confirm-modal");
+const $restartConfirmOk     = document.getElementById("restart-confirm-ok-btn");
+const $restartConfirmCancel = document.getElementById("restart-confirm-cancel-btn");
+const $restartConflictBox   = document.getElementById("restart-conflict-box");
+
 // System status banner
 // (removed — health is now shown per-tile via the composite health field)