Add knowledge graph visualization to dashboard

[dentity007]

What needs to be done

Add an interactive graph visualization to the web dashboard (web/index.html) using D3.js or vis.js. Show expert nodes, concept nodes, and relationship edges with color coding by type.

Why this matters

Seeing the knowledge graph visually is the most compelling way to understand what NeuralForge does. It would make the dashboard a showcase.

Where to look

• web/index.html, web/app.js, web/style.css
• GET /api/graph/stats and GET /api/graph/traverse for data

Acceptance criteria

• Interactive graph visualization renders in the dashboard
• Nodes colored by type (expert, concept, technique)
• Edges colored by type (agrees, contradicts, recommends)
• Click on node shows detail
• Works with 100+ nodes without performance issues