fix(feedback): show the operator reply only on the player's latest message

A reply was bound to 'the latest message that has a reply', so after the player
read a reply and sent a new (unanswered) message, the old reply kept showing as
'Ответ на ваше последнее сообщение'. Bind it to the single most-recent message
instead: sending any new message immediately drops the previous reply (the new
message has no reply yet), well before the one-week window. Client clears the
reply optimistically on submit; the mock mirrors it; inttest covers the case.

ui/src/screens/Feedback.svelte

@@ -71,7 +71,8 @@
       removeFile();
       sent = true;
       // The message is now under review: block resending until the operator handles it.
-      view = { canSend: false, blockedReason: 'pending', reply: view?.reply ?? null };
+      // A new message has no reply yet, so the previous operator reply stops showing.
+      view = { canSend: false, blockedReason: 'pending', reply: null };
     } catch (e) {
       handleError(e);
     } finally {