Phase 5: Add Neo4j graph database integration

- Add neo4j_manager.py with full graph operations support
- Data sync: projects, entities, relations to Neo4j
- Graph queries: shortest path, all paths, neighbors, common neighbors
- Graph algorithms: centrality analysis, community detection
- Add 11 new API endpoints for graph operations
- Update docker-compose.yml with Neo4j service
- Update requirements.txt with neo4j driver

docker-compose.yml

@@ -8,6 +8,30 @@ services:
     environment:
       - DEEPGRAM_API_KEY=${DEEPGRAM_API_KEY}
       - KIMI_API_KEY=${KIMI_API_KEY}
+      - NEO4J_URI=bolt://neo4j:7687
+      - NEO4J_USER=neo4j
+      - NEO4J_PASSWORD=${NEO4J_PASSWORD:-insightflow}
     volumes:
       - ./data:/app/data
     restart: unless-stopped
+    depends_on:
+      - neo4j
+
+  neo4j:
+    image: neo4j:5.15-community
+    ports:
+      - "7474:7474"  # HTTP
+      - "7687:7687"  # Bolt
+    environment:
+      - NEO4J_AUTH=neo4j/${NEO4J_PASSWORD:-insightflow}
+      - NEO4J_PLUGINS=["apoc", "gds"]
+      - NEO4J_dbms_security_procedures_unrestricted=apoc.*,gds.*
+      - NEO4J_dbms_security_procedures_allowlist=apoc.*,gds.*
+    volumes:
+      - neo4j_data:/data
+      - neo4j_logs:/logs
+    restart: unless-stopped
+
+volumes:
+  neo4j_data:
+  neo4j_logs: