Add pluggable graph drivers, service interfaces, and telemetry

[cpdata]

Summary

• add in-memory, SQLite, Memgraph, and Neo4j driver factory support and document the expanded configuration
• introduce REST and gRPC service layers plus test stubs so ingestion and retrieval can be exercised without external stacks
• wire observability utilities through the pipelines and scheduled tasks, refresh docker-compose, and promote the updated README set

Testing

• pytest (skipped: missing pydantic dependency in this sandbox)

---

https://chatgpt.com/codex/tasks/task_b_68ee1c9ee92c83218cbbebce8b0667b8