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-card.tsx

@@ -86,7 +86,7 @@ export function MessageCard({
                   deleted
                 </Badge>
               )}
-              {msg.type === "edited" && (
+              {(msg.type === "edited" || msg.edited_content) && (
                 <Badge
                   variant="outline"
                   className="text-[10px] px-1.5 py-0 h-4"
@@ -102,7 +102,10 @@ export function MessageCard({
                   "italic text-muted-foreground line-through",
               )}
             >
-              {renderMessageContent(msg.content, msg.metadata)}
+              {renderMessageContent(
+                msg.edited_content ?? msg.content,
+                msg.metadata,
+              )}
             </p>
             {(() => {
               const u = extractFirstImage(msg.metadata);