fix(bot-mode): fresh-room name uniquify counts every membership, not just the legacy scalar

With multi-group membership, a bot's meta carries groups[]; the create
dialog's taken-name scan must union all of them (botGroups) or a name only
present as a secondary membership could be reused and resurrect that room.

apps/desktop/src/plugins/hermes-bots/plugin.js

@@ -7447,9 +7447,7 @@ function CreateGroupChatDialog({ open, roster, onClose, onCreated }) {
     const taken = new Set(Object.keys($groupChats.get()))
 
     for (const meta of Object.values($botMeta.get() || {})) {
-      const existing = String(meta?.group || '').trim()
-
-      if (existing) {
+      for (const existing of botGroups(meta)) {
         taken.add(existing)
       }
     }