Group id fix

[prasmussen15]

Don't filter on group_id if no group_id is passed Fix regressions in node distance reranker

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[!IMPORTANT] Fix group_id filtering and node distance reranker logic across multiple files to ensure correct data retrieval and processing.

• Behavior:
  • Do not filter on group_id if no group_id is passed in retrieve_episodes() in graphiti.py and retrieve_episodes() in graph_data_operations.py.
  • Fix node distance reranker logic in node_distance_reranker() in search_utils.py to handle cases without a center node.
• Functions:
  • Change get_by_group_ids() in edges.py, nodes.py, and graphiti.py to accept only non-optional group_ids.
  • Update search() and _search() in graphiti.py to handle group_ids correctly.
• Misc:
  • Update DEFAULT_MODEL in openai_client.py to gpt-4o-mini.
  • Minor changes in podcast_runner.py to adjust message processing range.

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