CI workflow + Security Upgrades

[mattkjames7]

Description

• Distroless multi-stage build, non-root. Final stage is gcr.io/distroless/python3-debian13:nonroot; container runs as UID 65532. Image size 1.28 GB → 65.7 MB.
• Python 3.9 → 3.13 and refreshed PyPI deps (requests, urllib3, certifi, idna, prometheus-client) to reduce the overall number of CVEs.
• pyproject.toml cleanup. black/flake8/pre-commit moved to a dev group; PyYAML declared explicitly (was an undeclared transitive). Lockfile regenerated.
• New CI workflow (pull_request + workflow_dispatch) builds the image, runs it alongside the latest licensed Memgraph on a shared docker network, and asserts via tools/verify_metrics.py that all 95 expected metrics are exposed and that memory_usage reports a real non-zero value.

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Documentation checklist

• Add the documentation label tag
• Add the bug / feature label tag
• Write a release note, including added/changed clauses
  • Updated the Python version (3.13) and packages used to build the image and moved to a distroless container image build for a significantly smaller Docker image. #32
• Link the documentation PR here
  • [Documentation PR link]
• Tag someone from docs team in the comments