fix(security): a dismissed status announcement no longer hides the security nudge (#307)

SecurityBanner asked pickBanner whether another strip would show without
the dismissed set, so a dismissed Kuma announcement (often pinned for
weeks) still counted and suppressed the verify / backup nudge on every
device that had dismissed it. The dismissed set is now a shared jotai
atom (still persisted to localStorage) used by both banners. Adds a
Playwright regression.

Fixes #307

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

src/app/features/server-status/ServerStatusBanner.tsx

@@ -1,5 +1,5 @@
 import React, { useCallback, useEffect, useMemo, useState } from 'react';
-import { useAtomValue, useSetAtom } from 'jotai';
+import { useAtom, useAtomValue, useSetAtom } from 'jotai';
 import { MatrixClient, SyncState } from 'matrix-js-sdk';
 import { Box, Button, config, Icon, IconButton, Icons, IconSrc, Line, Text } from 'folds';
 import { ContainerColor } from '../../styles/ContainerColor.css';
@@ -7,21 +7,9 @@ import { useClientConfig } from '../../hooks/useClientConfig';
 import { useSyncState } from '../../hooks/useSyncState';
 import { useServerStatus } from '../../hooks/useServerStatus';
 import { ScreenSize, useScreenSizeContext } from '../../hooks/useScreenSize';
-import { serverStatusAtom } from '../../state/serverStatus';
+import { serverStatusAtom, statusDismissedAtom } from '../../state/serverStatus';
 import { pickBanner, resolveStatusPage, StatusBanner } from '../../utils/kumaStatus';
 
-const DISMISS_KEY = 'lotus-status-banner-dismissed';
-const DISMISS_MAX = 50;
-
-const readDismissed = (): string[] => {
-  try {
-    const v = JSON.parse(localStorage.getItem(DISMISS_KEY) ?? '[]');
-    return Array.isArray(v) ? v.filter((k): k is string => typeof k === 'string') : [];
-  } catch {
-    return [];
-  }
-};
-
 const bannerIcon = (b: StripContent): IconSrc => {
   if (b.kind === 'maintenance') return Icons.Setting;
   if (b.tone === 'Primary') return Icons.Info;
@@ -173,22 +161,14 @@ export function ServerStatusFeature({ mx }: { mx: MatrixClient }) {
 /** The logged-in app's status strip. */
 export function ServerStatusBanner() {
   const { status, syncLost } = useAtomValue(serverStatusAtom);
-  const [dismissed, setDismissed] = useState(readDismissed);
+  const [dismissed, dismissKey] = useAtom(statusDismissedAtom);
   const banner = pickBanner(status, {
     syncLost,
     where: 'client',
     dismissed: new Set(dismissed),
   });
   if (!banner) return null;
-  const dismiss = () => {
-    const next = [...dismissed.filter((k) => k !== banner.key), banner.key].slice(-DISMISS_MAX);
-    try {
-      localStorage.setItem(DISMISS_KEY, JSON.stringify(next));
-    } catch {
-      // storage unavailable — dismissed for this session only
-    }
-    setDismissed(next);
-  };
+  const dismiss = () => dismissKey(banner.key);
   return <StatusStrip banner={banner} onDismiss={dismiss} />;
 }