feat(desktop): tray Do-Not-Disturb + Launch-on-login toggle (P6-1 web)

- useTauriDnd + manualDndAtom: the native tray "Do Not Disturb" toggle
  (lotus-dnd-changed event) OR's into the notification quiet-gate in
  ClientNonUIFeatures (both invite + message notifiers), alongside Focus Assist.
- AutostartSetting in Settings → General (desktop-only): reads/sets
  plugin:autostart via invoke. Mirrors the window-chrome setting.
- Docs: LOTUS_FEATURES desktop section (Linux parity + DND + autostart),
  LOTUS_TODO P6-1 → [~], LOTUS_BUGS verification row.

Gates: tsc/eslint/prettier clean, build OK, 661 tests. Native side committed on
cinny-desktop:main (CI-compile-pending).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/pages/client/ClientNonUIFeatures.tsx

@@ -10,6 +10,7 @@ import {
   ThreadEvent,
 } from 'matrix-js-sdk';
 import { focusAssistActiveAtom } from '../../state/focusAssist';
+import { manualDndAtom } from '../../state/manualDnd';
 import { roomToUnreadAtom, unreadEqual, unreadInfoToUnread } from '../../state/room/roomToUnread';
 import LogoSVG from '../../../../public/res/lotus.png';
 import LogoUnreadSVG from '../../../../public/res/lotus-unread.png';
@@ -128,6 +129,7 @@ function InviteNotifications() {
   const [notificationSound] = useSetting(settingsAtom, 'isNotificationSounds');
   const [quietHoursEnabled] = useSetting(settingsAtom, 'quietHoursEnabled');
   const focusAssistActive = useAtomValue(focusAssistActiveAtom);
+  const manualDnd = useAtomValue(manualDndAtom);
   const [quietHoursStart] = useSetting(settingsAtom, 'quietHoursStart');
   const [quietHoursEnd] = useSetting(settingsAtom, 'quietHoursEnd');
   const [inviteSoundId] = useSetting(settingsAtom, 'inviteSoundId');
@@ -187,7 +189,9 @@ function InviteNotifications() {
   useEffect(() => {
     if (invites.length > perviousInviteLen && mx.getSyncState() === 'SYNCING') {
       const quietActive =
-        focusAssistActive || (quietHoursEnabled && isInQuietHours(quietHoursStart, quietHoursEnd));
+        focusAssistActive ||
+        manualDnd ||
+        (quietHoursEnabled && isInQuietHours(quietHoursStart, quietHoursEnd));
       if (!quietActive) {
         if (showNotifications && notificationPermission('granted')) {
           notify(invites.length - perviousInviteLen);
@@ -210,6 +214,7 @@ function InviteNotifications() {
     quietHoursStart,
     quietHoursEnd,
     focusAssistActive,
+    manualDnd,
     inviteSoundId,
   ]);
 
@@ -236,6 +241,7 @@ function MessageNotifications() {
   const [notificationSound] = useSetting(settingsAtom, 'isNotificationSounds');
   const [quietHoursEnabled] = useSetting(settingsAtom, 'quietHoursEnabled');
   const focusAssistActive = useAtomValue(focusAssistActiveAtom);
+  const manualDnd = useAtomValue(manualDndAtom);
   const [quietHoursStart] = useSetting(settingsAtom, 'quietHoursStart');
   const [quietHoursEnd] = useSetting(settingsAtom, 'quietHoursEnd');
   const [messageSoundId] = useSetting(settingsAtom, 'messageSoundId');
@@ -374,7 +380,9 @@ function MessageNotifications() {
       }
 
       const quietActive =
-        focusAssistActive || (quietHoursEnabled && isInQuietHours(quietHoursStart, quietHoursEnd));
+        focusAssistActive ||
+        manualDnd ||
+        (quietHoursEnabled && isInQuietHours(quietHoursStart, quietHoursEnd));
       if (quietActive) return;
 
       if (showNotifications && notificationPermission('granted')) {
@@ -409,6 +417,7 @@ function MessageNotifications() {
       quietHoursStart,
       quietHoursEnd,
       focusAssistActive,
+      manualDnd,
       messageSoundId,
     ],
   );