Add Stationery and Stationery Dark themes with notebook chrome.

Manila folders, ruled chat, post-it nav, and folder tabs; dark variant uses Catppuccin Mocha colors with muted stickies and soft glows.

src/app/features/room/RoomTimeline.tsx

@@ -2421,6 +2421,7 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
           ref={timelineContentRef}
           direction="Column"
           justifyContent="End"
+          data-chatroll=""
           style={{
             minHeight: '100%',
             padding: `${config.space.S600} 0`,