feat: Enforce exclusive auto-request (one client at a time)

Server is now source of truth for autoRequest. When a client enables it,
all other clients lose it. Broadcast includes autoRequest per client,
frontend syncs from server state on each torch-update.

server/services/sync-server.ts

@@ -78,7 +78,7 @@ export function startSyncServer() {
           const data = JSON.parse(message.toString())
 
           // Route to appropriate handler based on message type
-          if (data.type?.startsWith('torch-') || ['register', 'request', 'release', 'transfer', 'update-name'].includes(data.type)) {
+          if (data.type?.startsWith('torch-') || ['register', 'request', 'release', 'transfer', 'update-name', 'set-auto-request'].includes(data.type)) {
             handleTorchMessage(ws, data, broadcast)
           }
           // Git doesn't expect messages from client