fix(federation): use canonical message identity in reaction outbox payloads

Resolves canonical messageId (sourceMessageId for replicated messages,
local ID for originated messages) and includes messageHomeInstance so
the receiver can deterministically find the target message regardless
of which instance created it.

packages/server/src/ws/events.ts

@@ -12,6 +12,7 @@ import { sanitizeUser } from '../utils/sanitize.js';
 import { deleteAttachmentFiles } from '../utils/fileCleanup.js';
 import { resolveEmbeds, reResolveEmbeds, embedRowToEmbed } from '../utils/embedResolver.js';
 import { appendMutationLog, queueOutboxEvent, queueDmRelay } from '../utils/federationOutbox.js';
+import { getOurOrigin } from '../utils/federationAuth.js';
 
 /**
  * Re-evaluate SPEAK permission for all participants in voice channels
@@ -1127,6 +1128,8 @@ function handleReactionAdd(event: Record<string, unknown>, userId: string): void
     });
 
     // Federation: log reaction mutation and queue for relay
+    const canonicalMessageId = dmMsg.sourceMessageId || messageId;
+    const messageHomeInstance = dmMsg.sourceInstance || getOurOrigin();
     appendMutationLog(messageId, dmMsg.dmChannelId, 'reaction_add', JSON.stringify({
       userId,
       homeUserId: reactionUser?.homeUserId || userId,
@@ -1135,7 +1138,8 @@ function handleReactionAdd(event: Record<string, unknown>, userId: string): void
     }));
     queueOutboxEvent(reactionId, dmMsg.dmChannelId, 'reaction_add', JSON.stringify({
       reaction: {
-        messageId,
+        messageId: canonicalMessageId,
+        messageHomeInstance,
         userId,
         homeUserId: reactionUser?.homeUserId || userId,
         emoji,
@@ -1202,6 +1206,8 @@ function handleReactionRemove(event: Record<string, unknown>, userId: string): v
 
     // Federation: log reaction removal and queue for relay
     const removingUser = db.select().from(schema.users).where(eq(schema.users.id, userId)).get();
+    const canonicalMessageId = dmMsg.sourceMessageId || messageId;
+    const messageHomeInstance = dmMsg.sourceInstance || getOurOrigin();
     appendMutationLog(messageId, dmMsg.dmChannelId, 'reaction_remove', JSON.stringify({
       userId,
       homeUserId: removingUser?.homeUserId || userId,
@@ -1213,7 +1219,8 @@ function handleReactionRemove(event: Record<string, unknown>, userId: string): v
       'reaction_remove',
       JSON.stringify({
         reaction: {
-          messageId,
+          messageId: canonicalMessageId,
+          messageHomeInstance,
           userId,
           homeUserId: removingUser?.homeUserId || userId,
           emoji,