plugin XEP-0384: Fix reentrancy loop:

When `prepare_for_profile` is called during connection init, an infinite loop could happen
with 'get_session_manager` calling `prepare_for_profile`. A check is added to early exit
if the profile is already being prepared, avoiding this issue.

libervia/backend/plugins/plugin_xep_0384.py

@@ -2702,6 +2702,13 @@ class OMEMO:
         @param items_event: The event.
         @param profile: The profile this event belongs to.
         """
+        # Skip if session manager is already being built to prevent reentrancy loop
+        # (device list refresh during init triggers this handler again)
+        if profile in self.__session_manager_waiters:
+            log.debug(
+                f"Ignoring device list update for {profile} (session manager being built)"
+            )
+            return
 
         sender = cast(jid.JID, items_event.sender)
         items = cast(List[domish.Element], items_event.items)