feat: in-app update checker + Spinner import for General settings

- Add useTauriUpdater hook (check_for_update / install_update commands)
- Add AppUpdates section to General settings (Tauri-only, hidden on web)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/settings/general/General.tsx

@@ -26,6 +26,7 @@ import {
   PopOut,
   RectCords,
   Scroll,
+  Spinner,
   Switch,
   Text,
   toRem,
@@ -63,6 +64,7 @@ import { useMessageLayoutItems } from '../../../hooks/useMessageLayout';
 import { useMessageSpacingItems } from '../../../hooks/useMessageSpacing';
 import { useDateFormatItems } from '../../../hooks/useDateFormat';
 import { SequenceCardStyle } from '../styles.css';
+import { useTauriUpdater } from '../../../hooks/useTauriUpdater';
 
 type ThemeSelectorProps = {
   themeNames: Record<string, string>;
@@ -1476,6 +1478,46 @@ function Messages() {
   );
 }
 
+function AppUpdates() {
+  const { isTauri, status, check, install } = useTauriUpdater();
+  if (!isTauri) return null;
+
+  const description =
+    status.state === 'checking'
+      ? 'Checking for updates...'
+      : status.state === 'up-to-date'
+        ? 'Lotus Chat is up to date.'
+        : status.state === 'available'
+          ? `Update available: v${status.version}`
+          : status.state === 'installing'
+            ? 'Installing update, the app will restart shortly...'
+            : status.state === 'error'
+              ? `Update check failed: ${status.message}`
+              : 'Check for a new version of Lotus Chat.';
+
+  const after =
+    status.state === 'available' ? (
+      <Button size="300" radii="300" onClick={install}>
+        <Text size="B300">Install &amp; Restart</Text>
+      </Button>
+    ) : status.state === 'checking' || status.state === 'installing' ? (
+      <Spinner variant="Secondary" size="200" />
+    ) : (
+      <Button size="300" radii="300" variant="Secondary" onClick={check}>
+        <Text size="B300">Check</Text>
+      </Button>
+    );
+
+  return (
+    <Box direction="Column" gap="100">
+      <Text size="L400">App Updates</Text>
+      <SequenceCard className={SequenceCardStyle} variant="SurfaceVariant" direction="Column">
+        <SettingTile title="Check for Updates" description={description} after={after} />
+      </SequenceCard>
+    </Box>
+  );
+}
+
 type GeneralProps = {
   requestClose: () => void;
 };
@@ -1506,6 +1548,7 @@ export function General({ requestClose }: GeneralProps) {
               <Messages />
               <Privacy />
               <Calls />
+              <AppUpdates />
             </Box>
           </PageContent>
         </Scroll>