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/components/image-pack-view/ImagePackView.tsx

@@ -29,7 +29,7 @@ export function ImagePackView({ address, requestClose }: ImagePackViewProps) {
             </Chip>
           </Box>
           <Box shrink="No">
-            <IconButton onClick={requestClose} variant="Surface">
+            <IconButton onClick={requestClose} variant="Surface" aria-label="Close">
               <Icon src={Icons.Cross} />
             </IconButton>
           </Box>