refactor: update session loading method in SessionStore

- Replaced the call to `_load()` with `_ensure_loaded()` in the `has_any_sessions` method to improve clarity and ensure that session data is properly initialized before checking for existing sessions.

gateway/session.py

@@ -369,7 +369,7 @@ class SessionStore:
     
     def has_any_sessions(self) -> bool:
         """Check if any sessions have ever been created (across all platforms)."""
-        self._load()
+        self._ensure_loaded()
         return len(self._entries) > 1  # >1 because the current new session is already in _entries
     
     def get_or_create_session(