fix: wrap DM message deletion in transaction for atomicity

Matches the space message delete handler pattern. Prevents inconsistent
state if the server crashes between individual delete operations.

packages/server/src/ws/events.ts

@@ -993,20 +993,18 @@ function handleDmMessageDelete(event: Record<string, unknown>, userId: string):
   const dmAttachmentRows = db.select({ filename: schema.attachments.filename })
     .from(schema.attachments).where(eq(schema.attachments.dmMessageId, messageId)).all();
 
-  // Delete attachments linked to this DM message
-  db.delete(schema.attachments)
+  // Delete attachments, reactions, and message atomically
+  db.transaction((tx) => {
+    tx.delete(schema.attachments)
       .where(eq(schema.attachments.dmMessageId, messageId))
       .run();
-
-  // Delete reactions
-  db.delete(schema.dmReactions)
+    tx.delete(schema.dmReactions)
       .where(eq(schema.dmReactions.dmMessageId, messageId))
       .run();
-
-  // Delete message
-  db.delete(schema.dmMessages)
+    tx.delete(schema.dmMessages)
       .where(eq(schema.dmMessages.id, messageId))
       .run();
+  });
 
   // Clean up files from disk
   deleteAttachmentFiles(dmAttachmentRows);