fix(notifications): timed mutes are lifted by any Lotus device, not just the one that set them (#333)

A timed mute writes a server-side push rule (muted everywhere), but the
unmute timer lived in one browser's localStorage: close that laptop and
the room stayed muted on the phone until it was reopened, and forever
after a logout there. Timers now live in account data
(io.lotus.mute_timers: { timers: { [roomId]: unmuteAt } }). Every
client schedules from it, reschedules when it changes, and the first one
online after expiry unmutes. An indefinite mute clears a pending timer.
Local timers from before are migrated once.

Fixes #333

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/features/room-nav/RoomNavItem.tsx

@@ -80,7 +80,7 @@ import {
   setRoomNotificationPreference,
 } from '../../hooks/useRoomsNotificationPreferences';
 import { RoomNotificationModeSwitcher } from '../../components/RoomNotificationSwitcher';
-import { scheduleMuteTimer, unmuteRoom } from './muteTimers';
+import { clearMuteTimer, scheduleMuteTimer } from './muteTimers';
 import { getRoomCreatorsForRoomId, useRoomCreators } from '../../hooks/useRoomCreators';
 import { getRoomPermissionsAPI, useRoomPermissions } from '../../hooks/useRoomPermissions';
 import { InviteUserPrompt } from '../../components/invite-user-prompt';
@@ -381,9 +381,10 @@ const RoomNavItemMenu = forwardRef<HTMLDivElement, RoomNavItemMenuProps>(
           prevMode,
         ).catch(() => {});
         if (durationMs !== null) {
-          scheduleMuteTimer(room.roomId, durationMs, () => {
-            unmuteRoom(mx, room.roomId);
-          });
+          await scheduleMuteTimer(mx, room.roomId, durationMs).catch(() => {});
+        } else {
+          // An indefinite mute replaces any timed one.
+          await clearMuteTimer(mx, room.roomId);
         }
         requestClose();
       },