fix(status): any Lotus device clears an auto-expiring status, not just the one that set it (#300)

"Clear after 1 hour" lived in that device's localStorage, so a status
set on a laptop that was then closed stayed on the server until the
laptop opened Lotus again. The expiry is now also kept in account data
(io.lotus.status_expiry: { status_msg, expires_at }). Every device's
StatusExpiryMonitor clears the status when due, but only if it is still
the one that was set to expire (otherwise it just forgets the expiry).

Fixes #300

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

src/app/utils/statusExpiry.ts

@@ -0,0 +1,46 @@
+import { MatrixClient } from 'matrix-js-sdk';
+import { AccountDataEvent } from '../../types/matrix/accountData';
+import { getAccountData } from './room';
+
+/**
+ * [Gitea #300] The status message's auto-clear time, in account data so every
+ * Lotus device knows it. Before, only the device that set "clear after 1 hour"
+ * (localStorage) ever cleared it, and only while it was open.
+ */
+export type StatusExpiry = { statusMsg: string; expiresAt: number };
+
+/** Pure: parse `io.lotus.status_expiry` content. */
+export function parseStatusExpiry(content: unknown): StatusExpiry | undefined {
+  const c = content as { status_msg?: unknown; expires_at?: unknown } | undefined;
+  if (!c || typeof c.status_msg !== 'string' || typeof c.expires_at !== 'number') return undefined;
+  if (!c.status_msg || !Number.isFinite(c.expires_at)) return undefined;
+  return { statusMsg: c.status_msg, expiresAt: c.expires_at };
+}
+
+/**
+ * Pure: what to do with a due expiry. Clear the server status only if it is
+ * still the one that was set to expire; if it has since changed (e.g. on
+ * another device), just forget the expiry.
+ */
+export function statusExpiryAction(
+  entry: StatusExpiry | undefined,
+  currentStatusMsg: string | undefined,
+  now: number,
+): 'none' | 'clear' | 'forget' {
+  if (!entry || now < entry.expiresAt) return 'none';
+  return (currentStatusMsg ?? '') === entry.statusMsg ? 'clear' : 'forget';
+}
+
+export const readStatusExpiry = (mx: MatrixClient): StatusExpiry | undefined =>
+  parseStatusExpiry(getAccountData(mx, AccountDataEvent.LotusStatusExpiry)?.getContent());
+
+/** Record (or with no `expiresAt`, remove) the shared auto-clear time. */
+export async function writeStatusExpiry(
+  mx: MatrixClient,
+  statusMsg: string,
+  expiresAt?: number,
+): Promise<void> {
+  const content =
+    statusMsg && expiresAt !== undefined ? { status_msg: statusMsg, expires_at: expiresAt } : {};
+  await mx.setAccountData(AccountDataEvent.LotusStatusExpiry as never, content as never);
+}