feat(graphiti): Implement Graphiti client and related steps for episode ingestion and querying

- Added `graphiti_client.py` to manage the Graphiti client as a singleton.
- Created `ingest_episode_event_step.py` to handle episode ingestion from HTTP webhook events.
- Implemented `ingest_episode_step.py` for validating and enqueuing episode payloads via a POST request.
- Developed `query_graph_step.py` for performing semantic searches in the Graphiti Knowledge-Graph.
- Introduced an `__init__.py` file for the graphiti steps module.

pyproject.toml

@@ -22,5 +22,6 @@ dependencies = [
     "langchain>=0.3.0",  # LangChain framework
     "langchain-xai>=0.2.0",  # xAI integration for LangChain
     "langchain-core>=0.3.0",  # LangChain core
+    "graphiti-core>=0.28.0",  # Graphiti Knowledge-Graph
 ]