fix(manga): show force-resync result on mobile, not just desktop

`.resync-msg` (the admin Force-resync result) was display:none under 640px,
so mobile admins — who trigger resync from the overflow sheet — got no
success or error feedback. The element is already a sibling of `.action-row`
(not a child), so it survives the row being hidden; the only thing hiding it
was an explicit mobile rule. Drop that rule.

e2e: a mobile admin triggers Force resync from the overflow sheet and now
sees the "Metadata updated" result (written test-first against the hidden
element, then unhidden).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/routes/manga/[id]/+page.svelte

@@ -1243,9 +1243,9 @@
             display: none;
         }
 
-        .resync-msg {
-            display: none;
-        }
+        /* `.resync-msg` is a sibling of `.action-row`, not a child, so it
+           survives the row being hidden. Keep it visible on mobile: admins
+           trigger Force resync from the overflow sheet and need the result. */
 
         .continue {
             display: none;