feat(graph-service): add entity node handling and update Docker configurations

[paul-paliychuk]

:rocket:	This description was created by Ellipsis for commit a73f9443d67ae7749ce0ecef07f0bdd3d89dc4d4

Summary:

This PR updates the graph service by adding entity node handling, modifying DTOs, and updating Docker configurations.

Key points:

• Dockerfile: Added ENV PORT=8000 and modified CMD to use environment variable PORT.
• docker-compose.yml: Changed graph service to use zepai/graphiti:latest image and added PORT=8000 to environment variables.
• server/graph_service/dto/init.py: Added AddEntityNodeRequest to imports and __all__.
• server/graph_service/dto/common.py: Added uuid field to Message class.
• server/graph_service/dto/ingest.py: Added AddEntityNodeRequest class.
• server/graph_service/dto/retrieve.py: Removed search_type from SearchQuery and added center_node_uuid to GetMemoryRequest.
• server/graph_service/routers/ingest.py: Added /entity-node endpoint to handle AddEntityNodeRequest.
• server/graph_service/routers/retrieve.py: Added /episodes/{group_id} endpoint to retrieve episodes.
• server/graph_service/zep_graphiti.py: Added save_entity_node method to ZepGraphiti class.

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