feat(version): warn when the server was updated but not restarted (#898)

When the package is updated on disk but the long-lived server process is
not restarted, the new frontend bundle (served from disk) talks to the
old running backend. New DB-backed features then fail silently — e.g.
deleting/archiving a session appears to do nothing — because the new
schema/routes only take effect on restart.

Nothing currently detects this skew: useVersionCheck only compares the
frontend's build-time version against the latest GitHub release.

This exposes the running server's version (captured once at startup) via
/health, compares it to the frontend's build-time version in
useVersionCheck, and shows a "restart required" banner in the sidebar
(and a small indicator in the collapsed sidebar) when they differ.

- server: add `version` (RUNNING_VERSION, read once at startup) to /health
- useVersionCheck: return `restartRequired` / `runningVersion`
- SidebarFooter / SidebarCollapsed: surface a restart-required banner
- i18n: add `version.restartRequired` to all 10 sidebar locales

Verified with `tsc --noEmit` (client + server) and eslint.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Simos Mikelatos <simosmik@gmail.com>

src/components/sidebar/view/Sidebar.tsx

@@ -43,7 +43,7 @@ function Sidebar({
 }: SidebarProps) {
   const { t } = useTranslation(['sidebar', 'common']);
   const { isPWA } = useDeviceSettings({ trackMobile: false });
-  const { updateAvailable, latestVersion, currentVersion, releaseInfo, installMode } = useVersionCheck(
+  const { updateAvailable, restartRequired, latestVersion, currentVersion, releaseInfo, installMode } = useVersionCheck(
     'siteboon',
     'claudecodeui',
   );
@@ -224,6 +224,7 @@ function Sidebar({
           onExpand={handleExpandSidebar}
           onShowSettings={onShowSettings}
           updateAvailable={updateAvailable}
+          restartRequired={restartRequired}
           onShowVersionModal={() => setShowVersionModal(true)}
           t={t}
         />
@@ -296,6 +297,7 @@ function Sidebar({
             onCreateProject={() => setShowNewProject(true)}
             onCollapseSidebar={handleCollapseSidebar}
             updateAvailable={updateAvailable}
+            restartRequired={restartRequired}
             releaseInfo={releaseInfo}
             latestVersion={latestVersion}
             currentVersion={currentVersion}