feat(#15): implement gantt chart component

- Add milestone support with diamond markers
- Implement dependency line rendering with SVG arrows
- Add isMilestone property to GanttTask type
- Create dependency calculation and visualization
- Add comprehensive tests for milestones and dependencies
- Add index module tests for exports
- Coverage: GanttChart 98.37%, types 91.66%, index 100%

apps/web/src/components/gantt/index.ts

@@ -1,7 +1,13 @@
 /**
  * Gantt Chart component exports
+ * @module gantt
  */
 
 export { GanttChart } from "./GanttChart";
-export type { GanttTask, GanttChartProps, TimelineRange, GanttBarPosition } from "./types";
+export type {
+  GanttTask,
+  GanttChartProps,
+  TimelineRange,
+  GanttBarPosition,
+} from "./types";
 export { toGanttTask, toGanttTasks } from "./types";