fix(a11y,bug): aria-labels on dialogs/buttons, useAlive GIF guard, typing timer fix

A11y:
- Add aria-label Close to RoomTopicViewer, ImagePackView close buttons
- Add aria-label Cancel to LeaveRoomPrompt cancel button
- Add aria-label to Send, Reply, Thread, Edit, React, Search, Mute, Download buttons
- Fix aria-pressed -> aria-expanded + aria-haspopup on menu anchor triggers
- Add aria-label to username/password auth inputs

BUG-21: Add useAlive unmount guard to handleGifSelect error path in RoomInput
BUG-22: Fix typing status timer accumulation with typingTimerRef

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

src/app/hooks/useTypingStatusUpdater.ts

@@ -6,6 +6,7 @@ type TypingStatusUpdater = (typing: boolean) => void;
 
 export const useTypingStatusUpdater = (mx: MatrixClient, roomId: string): TypingStatusUpdater => {
   const statusSentTsRef = useRef<number>(0);
+  const typingTimerRef = useRef<ReturnType<typeof setTimeout> | undefined>(undefined);
 
   const sendTypingStatus: TypingStatusUpdater = useMemo(() => {
     statusSentTsRef.current = 0;
@@ -19,9 +20,10 @@ export const useTypingStatusUpdater = (mx: MatrixClient, roomId: string): Typing
         const sentTs = Date.now();
         statusSentTsRef.current = sentTs;
 
-        // Don't believe server will timeout typing status;
-        // Clear typing status after timeout if already not;
-        setTimeout(() => {
+        // Cancel any previous pending timeout before scheduling a new one
+        if (typingTimerRef.current !== undefined) clearTimeout(typingTimerRef.current);
+        typingTimerRef.current = setTimeout(() => {
+          typingTimerRef.current = undefined;
           if (statusSentTsRef.current === sentTs) {
             mx.sendTyping(roomId, false, TYPING_TIMEOUT_MS);
             statusSentTsRef.current = 0;