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>

app/(dashboard)/dashboard/page.tsx

@@ -17,8 +17,8 @@ export default function DashboardPage() {
   // Calculate statistics
   const stats = {
     totalProjects: projects?.length || 0,
-    activeProjects: projects?.filter(p => p.status === 'Active').length || 0,
-    archivedProjects: projects?.filter(p => p.status === 'Archived').length || 0,
+    activeProjects: projects?.length || 0, // TODO: Add status field to Project model
+    archivedProjects: 0, // TODO: Add status field to Project model
   };
 
   // Get recent projects (sort by creation time, take first 5)
@@ -142,12 +142,10 @@ export default function DashboardPage() {
                   <div className="space-y-1">
                     <div className="flex items-center gap-2">
                       <h3 className="font-semibold">{project.name}</h3>
-                      <Badge variant={project.status === 'Active' ? 'default' : 'secondary'}>
-                        {project.status}
-                      </Badge>
+                      <Badge variant="default">{project.key}</Badge>
                     </div>
                     <p className="text-sm text-muted-foreground">
-                      {project.key} • {project.description || 'No description'}
+                      {project.description || 'No description'}
                     </p>
                   </div>
                   <div className="text-sm text-muted-foreground">