feat: multi-WebSocket connection manager for instance federation

Refactor the WebSocket layer from a singleton connection to a connection
map supporting N concurrent instances. Each connection has its own
heartbeat worker, reconnect state, and token. Stores are now
instance-aware: serverStore merges servers by origin, chatStore routes
API calls through the correct client, and instanceStore triggers WS
connect/disconnect on add/remove. DM, social, and voice events remain
home-only.

packages/web/src/components/chat/Message.tsx

@@ -60,9 +60,9 @@ export function Message({ message, isCompact, isFirstInGroup }: MessageProps) {
   const toggleReaction = (emoji: string) => {
     const hasReacted = message.reactions?.some(r => r.userId === currentUser?.id && r.emoji === emoji);
     if (hasReacted) {
-      removeReaction(message.id, emoji);
+      removeReaction(message.id, emoji, channelKey);
     } else {
-      addReaction(message.id, emoji);
+      addReaction(message.id, emoji, channelKey);
     }
   };