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.test.ts

@@ -0,0 +1,23 @@
+import { describe, it, expect } from "vitest";
+import {
+  GanttChart,
+  toGanttTask,
+  toGanttTasks,
+} from "./index";
+
+describe("Gantt module exports", () => {
+  it("should export GanttChart component", () => {
+    expect(GanttChart).toBeDefined();
+    expect(typeof GanttChart).toBe("function");
+  });
+
+  it("should export toGanttTask helper", () => {
+    expect(toGanttTask).toBeDefined();
+    expect(typeof toGanttTask).toBe("function");
+  });
+
+  it("should export toGanttTasks helper", () => {
+    expect(toGanttTasks).toBeDefined();
+    expect(typeof toGanttTasks).toBe("function");
+  });
+});