feat(a11y): comprehensive icon button label sweep — 60+ remaining buttons labeled

C-1 complete sweep across all components and features:
- Call controls: mic mute/unmute, deafen/undeafen, video, screenshare, chat
- RoomInput: dismiss reply, attach file, sticker, emoji, GIF, location, toolbar
- Media viewers: close in image/pdf/text viewers and editors
- Settings dialogs: close buttons in all room/space/common settings panels
- Lobby: back, toggle member list, scroll to top, pack add/remove
- Auth: server picker, UIA flow cancel
- Upload cards: cancel uploads
- URL preview: prev/next buttons
- Members drawer: close + scroll to top
- RoomViewHeader: back, start call, toggle member list

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

src/app/features/room/CallChatView.tsx

@@ -41,7 +41,7 @@ export function CallChatView() {
               }
             >
               {(triggerRef) => (
-                <IconButton ref={triggerRef} variant="Surface" onClick={handleClose}>
+                <IconButton ref={triggerRef} variant="Surface" onClick={handleClose} aria-label="Close call chat">
                   <Icon src={Icons.Cross} />
                 </IconButton>
               )}