Update dependency neo4j to ==5.28.*

Author: renovate[bot]

requirements.txt

@@ -25,7 +25,7 @@ optuna==4.3.*
 umap-learn==0.5.* # Dimensionality reduction to visualize node embeddings in 2D
 
 # --- Database connector ---
-neo4j==5.23.*
+neo4j==5.28.*
 
 # --- Native/scientific packages (may require compilation) ---
 # These are included but may cause install errors in pip/venv