fix(messages): merge partial WS updates + display edited content

message_updated broadcasts only {id, edited_content, edited_at} (+ reset
ai_* fields), but the frontend replaced the whole cached record, wiping
username/content/channel_id/created_at -> blank cards and the
'the channel_id of undefined' crash on /messages. Merge partials over the
existing record (list + detail), make list-patching channel-filter aware,
show edited content/badge, and fix the message_updated WS type.

Also broadcast type:'edited' + ai reset in message_updated so the live UI
matches the DB update.

services/frontend/src/components/messages/message-detail-view.tsx

@@ -44,8 +44,10 @@ export function MessageDetailView({
 
       {/* Content */}
       <div className="text-sm text-text-primary/90 leading-relaxed mb-4 whitespace-pre-wrap">
-        {renderMessageContent(message.content, message.metadata) ||
-          "(no text content)"}
+        {renderMessageContent(
+          message.edited_content ?? message.content,
+          message.metadata,
+        ) || "(no text content)"}
       </div>
 
       {/* Attachments */}