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/Controls.tsx

@@ -33,6 +33,7 @@ export function MicrophoneButton({ enabled, onToggle }: MicrophoneButtonProps) {
           radii="400"
           size="400"
           onClick={() => onToggle()}
+          aria-label={enabled ? 'Turn Off Microphone' : 'Turn On Microphone'}
           outlined
         >
           <Icon size="400" src={enabled ? Icons.Mic : Icons.MicMute} filled={!enabled} />
@@ -65,6 +66,7 @@ export function SoundButton({ enabled, onToggle }: SoundButtonProps) {
           radii="400"
           size="400"
           onClick={() => onToggle()}
+          aria-label={enabled ? 'Undeafen' : 'Deafen'}
           outlined
         >
           <Icon
@@ -142,6 +144,8 @@ export function ScreenShareButton({ enabled, onToggle }: ScreenShareButtonProps)
           radii="400"
           size="400"
           onClick={() => onToggle()}
+          aria-label={enabled ? 'Stop Video' : 'Start Video'}
+          aria-label={enabled ? 'Stop Screenshare' : 'Start Screenshare'}
           outlined
         >
           <Icon size="400" src={Icons.ScreenShare} filled={enabled} />
@@ -172,6 +176,8 @@ export function ChatButton() {
           radii="400"
           size="400"
           onClick={() => setChat(!chat)}
+          aria-label={chat ? 'Close Chat' : 'Open Chat'}
+          aria-pressed={chat}
           outlined
         >
           <Icon size="400" src={Icons.Message} filled={chat} />