Enhance: Improve graph edge visualization with smooth curves and better arrow visibility

- Replace angular paths with smooth cubic Bézier curves connecting directly to node edges
- Improve path separation with wider curve offset range (±105px) to prevent confusing overlaps
- Add color-matched arrow markers for each relationship type (9x9px with subtle shadows)
- Position labels 25px perpendicular to path using Bézier tangent mathematics
- Increase edge stroke width to 3px with subtle glow filter for better depth
- Extend control points to 60% of distance (max 150px) for more graceful curves

Author: Patel230