fix(federation): fix reaction relay using wrong ID for message lookup

Reaction outbox events used reactionId (add) or a composite dedup key
(remove) as the event messageId. The receiver looked up dm_messages by
sourceMessageId = event.messageId, which never matched because it was
searching for a reactionId, not the actual message ID.

Fix: include the actual DM messageId in the reaction payload JSON.
The receiver now uses event.reaction.messageId for the lookup, with
fallback to event.messageId for backward compatibility.

packages/server/src/ws/events.ts

@@ -1135,6 +1135,7 @@ function handleReactionAdd(event: Record<string, unknown>, userId: string): void
     }));
     queueOutboxEvent(reactionId, dmMsg.dmChannelId, 'reaction_add', JSON.stringify({
       reaction: {
+        messageId,
         userId,
         homeUserId: reactionUser?.homeUserId || userId,
         emoji,
@@ -1212,6 +1213,7 @@ function handleReactionRemove(event: Record<string, unknown>, userId: string): v
       'reaction_remove',
       JSON.stringify({
         reaction: {
+          messageId,
           userId,
           homeUserId: removingUser?.homeUserId || userId,
           emoji,