feat: add backend sticker message relay and fix frontend handler

- Add stickers.setMode and stickers.mode handlers to WebSocket manager
  so messages relay between frontend and vote-app via session broadcast
- Fix frontend to read message.data.mode (matching broadcastEvent format)
- Bump version to 0.8.1

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/utils/websocket-manager.js

@@ -142,6 +142,30 @@ class WebSocketManager {
         }
         break;
         
+      case 'stickers.setMode':
+        if (!clientInfo.authenticated) {
+          this.sendError(ws, 'Not authenticated');
+          return;
+        }
+        if (message.data?.mode && ['auto', 'show', 'hide'].includes(message.data.mode)) {
+          clientInfo.subscribedSessions.forEach(sessionId => {
+            this.broadcastEvent('stickers.setMode', message.data, sessionId);
+          });
+        }
+        break;
+
+      case 'stickers.mode':
+        if (!clientInfo.authenticated) {
+          this.sendError(ws, 'Not authenticated');
+          return;
+        }
+        if (message.mode && ['auto', 'show', 'hide'].includes(message.mode)) {
+          clientInfo.subscribedSessions.forEach(sessionId => {
+            this.broadcastEvent('stickers.mode', { mode: message.mode }, sessionId);
+          });
+        }
+        break;
+
       default:
         this.sendError(ws, `Unknown message type: ${message.type}`);
     }