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/css/modals.css

@@ -102,6 +102,48 @@ button.btn-reboot:hover:not(:disabled) {
   background-color: #529E7E;
 }
 
+/* Restart = AMBER (manual restart action) */
+.btn-restart-amber {
+  background-color: #b87d00;
+  color: #fff;
+}
+
+.btn-restart-amber:hover:not(:disabled) {
+  background-color: #9a6800;
+}
+
+/* Restart conflict warning box */
+.restart-conflict-box {
+  background-color: rgba(180, 100, 0, 0.12);
+  border-left: 3px solid #c97a00;
+  border-radius: 6px;
+  padding: 12px 14px;
+  margin-bottom: 14px;
+}
+
+.restart-conflict-title {
+  font-size: 0.88rem;
+  font-weight: 700;
+  color: #e69000;
+  margin: 0 0 6px 0;
+}
+
+.restart-conflict-desc {
+  font-size: 0.83rem;
+  color: var(--text-secondary);
+  line-height: 1.5;
+  margin: 0;
+}
+
+/* Reboot error card actions row */
+.reboot-error-actions {
+  display: flex;
+  gap: 12px;
+  justify-content: center;
+  flex-wrap: wrap;
+  margin-top: 20px;
+}
+
 .btn-save {
   background-color: var(--yellow);
   color: #0A1A10;