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/call-status/CallControl.tsx

@@ -62,6 +62,7 @@ function SoundButton({ enabled, onToggle, disabled }: SoundButtonProps) {
           radii="300"
           size="300"
           onClick={() => onToggle()}
+          aria-label={enabled ? 'Undeafen' : 'Deafen'}
           outlined
           disabled={disabled}
         >
@@ -99,6 +100,7 @@ function VideoButton({ enabled, onToggle, disabled }: VideoButtonProps) {
           radii="300"
           size="300"
           onClick={() => onToggle()}
+          aria-label={enabled ? 'Stop Video' : 'Start Video'}
           outlined
           disabled={disabled}
         >
@@ -136,6 +138,7 @@ function ScreenShareButton({ enabled, onToggle, disabled }: ScreenShareButtonPro
           radii="300"
           size="300"
           onClick={onToggle}
+          aria-label={enabled ? 'Stop Screenshare' : 'Start Screenshare'}
           outlined
           disabled={disabled}
         >