✨ feat: add dependency graph view for task visualization

Add a new interactive graph view alongside the kanban board for visualizing
task dependencies. The graph view uses React Flow with dagre auto-layout to
display tasks as nodes connected by dependency edges.

Key features:
- Toggle between kanban and graph view via new control buttons
- Custom TaskNode component matching existing card styling/themes
- Animated edges that flow when tasks are in progress
- Status-aware node colors (backlog, in-progress, waiting, verified)
- Blocked tasks show lock icon with dependency count tooltip
- MiniMap for navigation in large graphs
- Zoom, pan, fit-view, and lock controls
- Horizontal/vertical layout options via dagre
- Click node to view details, double-click to edit
- Respects all 32 themes via CSS variables
- Reduced motion support for animations

New dependencies: @xyflow/react, dagre

apps/ui/src/components/views/graph-view/index.ts

@@ -0,0 +1,4 @@
+export { GraphView } from './graph-view';
+export { GraphCanvas } from './graph-canvas';
+export { TaskNode, DependencyEdge, GraphControls, GraphLegend } from './components';
+export { useGraphNodes, useGraphLayout, type TaskNode as TaskNodeType, type DependencyEdge as DependencyEdgeType } from './hooks';