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/RoomInput.tsx

@@ -629,6 +629,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                 >
                   <IconButton
                     onClick={() => setReplyDraft(undefined)}
+                    aria-label="Dismiss reply"
                     variant="SurfaceVariant"
                     size="300"
                     radii="300"
@@ -661,6 +662,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
           before={
             <IconButton
               onClick={() => pickFile('*')}
+              aria-label="Attach file"
               variant="SurfaceVariant"
               size="300"
               radii="300"
@@ -674,6 +676,8 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                 variant="SurfaceVariant"
                 size="300"
                 radii="300"
+                aria-label={toolbar ? 'Hide formatting toolbar' : 'Show formatting toolbar'}
+                aria-pressed={toolbar}
                 onClick={() => setToolbar(!toolbar)}
               >
                 <Icon src={toolbar ? Icons.AlphabetUnderline : Icons.Alphabet} />
@@ -714,6 +718,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                     {!hideStickerBtn && (
                       <IconButton
                         aria-pressed={emojiBoardTab === EmojiBoardTab.Sticker}
+                        aria-label="Insert sticker"
                         onClick={() => setEmojiBoardTab(EmojiBoardTab.Sticker)}
                         variant="SurfaceVariant"
                         size="300"
@@ -727,6 +732,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                     )}
                     <IconButton
                       ref={emojiBtnRef}
+                      aria-label="Insert emoji"
                       aria-pressed={
                         hideStickerBtn ? !!emojiBoardTab : emojiBoardTab === EmojiBoardTab.Emoji
                       }
@@ -768,6 +774,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
                     >
                       <IconButton
                         ref={gifBtnRef}
+                        aria-label="Insert GIF"
                         aria-pressed={gifOpen}
                         onClick={() => setGifOpen(!gifOpen)}
                         variant="SurfaceVariant"
@@ -797,6 +804,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
               )}
               <IconButton
                 onClick={handleShareLocation}
+                aria-label="Share location"
                 variant="SurfaceVariant"
                 size="300"
                 radii="300"