Fix: Neo4j 5.26.0 (APOC available) + correct graphrag schema from seeder

Fix APOC: keep plugins in /opt/neo4j/plugins (not /data), use direct neo4j_conn for graph stats

Fix 500: use 'or' fallback for env vars, guard eligible-patient query against Neo4j not ready

Fix backend crash: make Neo4jGraph lazy-init in graphrag.py — was failing at import time

Initial deployment: ClinicalMatch AI v2.0 — FHIR R4 · MCP (9 tools) · A2A workflow · SHARP compliance · 100k synthetic patients · Neo4j graph · GraphRAG chatbot