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/common-settings/members/Members.tsx

@@ -161,7 +161,7 @@ export function Members({ requestClose }: MembersProps) {
             </Text>
           </Box>
           <Box shrink="No">
-            <IconButton onClick={requestClose} variant="Surface">
+            <IconButton onClick={requestClose} variant="Surface" aria-label="Close">
               <Icon src={Icons.Cross} />
             </IconButton>
           </Box>
@@ -278,6 +278,7 @@ export function Members({ requestClose }: MembersProps) {
               >
                 <IconButton
                   onClick={() => virtualizer.scrollToOffset(0)}
+                  aria-label="Scroll to top"
                   variant="Surface"
                   radii="Pill"
                   outlined