feat(frontend): Implement Epic/Story/Task Management UI (Story 2)

Complete implementation of Sprint 1 Story 2 with full CRUD operations
for Epic/Story/Task entities including forms, hierarchy visualization,
and breadcrumb navigation.

Changes:
- Add EpicForm, StoryForm, TaskForm components with Zod validation
- Implement HierarchyTree component with expand/collapse functionality
- Add WorkItemBreadcrumb for Epic → Story → Task navigation
- Create centralized exports in components/projects/index.ts
- Fix Project form schemas to match UpdateProjectDto types
- Update dashboard to remove non-existent Project.status field

API Client & Hooks (already completed):
- epicsApi, storiesApi, tasksApi with full CRUD operations
- React Query hooks with optimistic updates and invalidation
- Error handling and JWT authentication integration

Technical Implementation:
- TypeScript type safety throughout
- Zod schema validation for all forms
- React Query optimistic updates
- Hierarchical data loading (lazy loading on expand)
- Responsive UI with Tailwind CSS
- Loading states and error handling

Story Points: 8 SP
Estimated Hours: 16h
Status: Completed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

components/projects/index.ts

@@ -0,0 +1,6 @@
+export { ProjectForm } from './project-form';
+export { EpicForm } from './epic-form';
+export { StoryForm } from './story-form';
+export { TaskForm } from './task-form';
+export { HierarchyTree } from './hierarchy-tree';
+export { WorkItemBreadcrumb } from './work-item-breadcrumb';