Bug fixes, security hardening, and performance improvements

- BUG-16: Fixed pagination deadlock (fetching flag stuck on error path)
- BUG-17: Fixed absoluteIndex===0 falsy check skipping unread jump
- BUG-19: Fixed mEvt.getRoomId()! non-null assertion crash
- BUG-20: Wrapped getSettings()/setSettings() in try/catch for corrupt localStorage
- SEC: Replaced randomStr() Math.random() with crypto.getRandomValues() CSPRNG
- SEC: Fixed afterLoginRedirectPath open redirect validation
- SEC: Narrowed OSM iframe sandbox to scripts-only (removed allow-same-origin)
- Perf-2: Memoized selectAtom in useSetting (prevented new atom ref per render)
- Perf-4: Fixed typingMembers setTimeout leak (tracked timers per user/room)
- Perf-8: Memoized getChatBg() result in RoomView (not inline in JSX)
- Perf-12: Replaced body.class * font-family with body.class (inherited)
- Perf-15: Memoized typingNames array chain in RoomViewTyping
- Perf-9: Added blob URL cleanup useEffect in AudioContent
- BUG: Fixed forEach(async) -> Promise.all in useCommands join handler
- BUG: Fixed useCompositionEndTracking missing dependency array
- A11y: Fixed spoiler button aria-pressed + keyboard handler
- A11y: Added aria-label to Send message button
- Build: Set sourcemap:false, removed netlify.toml from copyFiles

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/state/settings.ts

@@ -102,17 +102,19 @@ const defaultSettings: Settings = {
   pttKey: 'Space',
 };
 
-export const getSettings = () => {
-  const settings = localStorage.getItem(STORAGE_KEY);
-  if (settings === null) return defaultSettings;
-  return {
-    ...defaultSettings,
-    ...(JSON.parse(settings) as Settings),
-  };
+export const getSettings = (): Settings => {
+  try {
+    const settings = localStorage.getItem(STORAGE_KEY);
+    if (settings === null) return defaultSettings;
+    return { ...defaultSettings, ...(JSON.parse(settings) as Settings) };
+  } catch {
+    localStorage.removeItem(STORAGE_KEY);
+    return defaultSettings;
+  }
 };
 
 export const setSettings = (settings: Settings) => {
-  localStorage.setItem(STORAGE_KEY, JSON.stringify(settings));
+  try { localStorage.setItem(STORAGE_KEY, JSON.stringify(settings)); } catch { /* quota */ }
 };
 
 const baseSettings = atom<Settings>(getSettings());