Feature/custody hash graph

[Saranyadharani]

🔗 Chain of Custody Visualizer with Immutable Hash Graph

Problem

Current chain of custody shows text entries only, lacks visual mapping between evidence states.

Solution

Added interactive directed graph with nodes, edges, hash verification, and gap detection.

Features

• Interactive Graph - Nodes with timestamps, handlers, actions, hash fingerprints
• Color-coded Edges - Red for gaps >4 hours, Blue for normal
• Zoom & Pan - Scroll to zoom, drag to pan
• Click Nodes - View detailed metadata without page reload
• Real-time Stats - Total steps, verified nodes, gap count

Files Added

• styles/custody.css - Forensic-themed styling
• js/custodyGraph.js - Graph rendering with zoom/pan
• js/hashVerification.js - Hash integrity utilities

Files Modified

• html/dashboard.html - Added custody section
• js/dashboard.js - Graph initialization

Testing ✅

• Graph renders after analysis
• Node click shows details panel
• Red edges highlight gaps
• Zoom/pan works
• Dark/light theme compatible

Closes #152