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/types/matrix/accountData.ts

@@ -26,6 +26,10 @@ export enum AccountDataEvent {
   // [Gitea #104] Synced subset of the Lotus Settings object (utils/settingsSync).
   LotusSettings = 'io.lotus.settings',
 
+  // [Gitea #333] Timed mutes: { timers: { [roomId]: unmuteAt } }, so any Lotus
+  // device can lift a mute set on another.
+  LotusMuteTimers = 'io.lotus.mute_timers',
+
   SecretStorageDefaultKey = 'm.secret_storage.default_key',
 
   CrossSigningMaster = 'm.cross_signing.master',