feat: Interactive Motif Census - subgraph pattern analysis with significance testing

Replace static motif documentation with full interactive tool:
- Enumerate 6 motif types (triangle, wedge, 3-star, square, diamond, K4)
- 8 graph presets (Karate Club, social, star, ring, random, complete, bipartite, scale-free)
- Custom edge list input
- Canvas force-directed graph with motif instance highlighting
- Census bar chart visualization
- Erdos-Renyi random graph ensemble comparison with z-score significance profile
- Autonomous proactive insights engine (clustering, hub detection, network type classification)
- Interactive: drag nodes, pan/zoom, click motif chips to highlight instances

Author: sauravbhattacharya001