Add Memgraph as Graph provider

[antejavor]

This PR adds Memgraph as Graph provider

• Add Memgraph KG
• Add Memgraph KG integration test
• Add test runner helper
• Make integration test work
• Write a small example of MiniRag and Memgraph
• Fix debug

[antejavor]

Integration tests seem to work correctly:

(MiniRAG) ➜  tests git:(add-memgraph) ✗ python run_memgraph_tests.py --verbose
2025-07-04 09:39:28 - pipmaster.package_manager - INFO - Targeting pip associated with Python: /Users/antejavor/repos/MiniRAG/.venv/bin/python | Command base: /Users/antejavor/repos/MiniRAG/.venv/bin/python -m pip
2025-07-04 09:39:28 - pipmaster.package_manager - INFO - Targeting pip associated with Python: /Users/antejavor/repos/MiniRAG/.venv/bin/python | Command base: /Users/antejavor/repos/MiniRAG/.venv/bin/python -m pip
2025-07-04 09:39:28 - pipmaster.async_package_manager - INFO - [Async] Initialized for Python: /Users/antejavor/repos/MiniRAG/.venv/bin/python
🚀 Memgraph Integration Test Runner
==================================================
Memgraph URI: bolt://localhost:7687

📡 Checking Memgraph connection...
✅ Memgraph connection successful

🧪 Running integration tests...
Running command: python -m pytest test_memgraph.py -v -m integration --tb=short
============================================================================================================================================================= test session starts =============================================================================================================================================================
platform darwin -- Python 3.13.1, pytest-8.4.1, pluggy-1.6.0 -- /Users/antejavor/repos/MiniRAG/.venv/bin/python
cachedir: .pytest_cache
rootdir: /Users/antejavor/repos/MiniRAG
configfile: pyproject.toml
plugins: asyncio-1.0.0
asyncio: mode=Mode.STRICT, asyncio_default_fixture_loop_scope=None, asyncio_default_test_loop_scope=function
collected 10 items                                                                                                                                                                                                                                                                                                                            

test_memgraph.py::TestMemgraphIntegration::test_memgraph_connection PASSED                                                                                                                                                                                                                                                              [ 10%]
test_memgraph.py::TestMemgraphIntegration::test_node_operations PASSED                                                                                                                                                                                                                                                                  [ 20%]
test_memgraph.py::TestMemgraphIntegration::test_edge_operations PASSED                                                                                                                                                                                                                                                                  [ 30%]
test_memgraph.py::TestMemgraphIntegration::test_node_degree_operations PASSED                                                                                                                                                                                                                                                           [ 40%]
test_memgraph.py::TestMemgraphIntegration::test_node_edges_retrieval PASSED                                                                                                                                                                                                                                                             [ 50%]
test_memgraph.py::TestMemgraphIntegration::test_type_operations PASSED                                                                                                                                                                                                                                                                  [ 60%]
test_memgraph.py::TestMemgraphIntegration::test_knowledge_graph_retrieval PASSED                                                                                                                                                                                                                                                        [ 70%]
test_memgraph.py::TestMemgraphIntegration::test_error_handling PASSED                                                                                                                                                                                                                                                                   [ 80%]
test_memgraph.py::TestMemgraphIntegration::test_complex_graph_operations PASSED                                                                                                                                                                                                                                                         [ 90%]
test_memgraph.py::test_storage_lifecycle PASSED