Foro: mover tema entre foros (moderadores)

- lib/forum-write.ts: moveTopic (forum_id + moved=1). lib/forum.ts: listForumsForMove.
- API /api/forum/moderate: acción 'move' con forumId, validando foro destino visible
  y distinto del actual.
- TopicModBar: selector «Mover a» con los foros visibles (excl. el actual); tras mover,
  redirige al foro destino.
- i18n es/en: Forum.moveTopic.

Verificado: build OK, move 401 sin sesión, /forum 200.

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

web-next/messages/en.json

@@ -293,7 +293,8 @@
     "noResults": "No results for “{query}”.",
     "resultsCount": "{count} result(s) for “{query}”.",
     "in": "in",
-    "replyOnLastPage": "Go to the last page to reply"
+    "replyOnLastPage": "Go to the last page to reply",
+    "moveTopic": "Move to"
   },
   "Admin": {
     "title": "Admin panel",