fix(mobile): make media gallery and members panel accessible on mobile

MediaGallery: fixed panel now goes full-width (100%) on mobile instead
of the inaccessible 320px right sidebar. Added 'Media Gallery' MenuItem
to RoomMenu (visible only on mobile) so users can open it from the
More Options (···) button.

MembersDrawer: removed ScreenSize.Desktop gate in Room.tsx so it now
renders on mobile too. CSS media query (≤750px) makes it position:fixed
inset:0 width:100% on mobile instead of the 266px desktop sidebar.
Added 'Members' MenuItem to RoomMenu for mobile access.

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

src/app/features/room/Room.tsx

@@ -78,9 +78,11 @@ export function Room() {
             <CallChatView />
           </>
         )}
-        {!callView && screenSize === ScreenSize.Desktop && isDrawer && (
+        {!callView && isDrawer && (
           <>
-            <Line variant="Background" direction="Vertical" size="300" />
+            {screenSize === ScreenSize.Desktop && (
+              <Line variant="Background" direction="Vertical" size="300" />
+            )}
             <MembersDrawer key={room.roomId} room={room} members={members} />
           </>
         )}