feat(frontend): Implement Epic management page with full CRUD operations

Add comprehensive Epic management functionality at /projects/{projectId}/epics route.

Changes:
- Created EpicForm component with validation (title, description, priority, estimated hours)
- Implemented Epics list page with Create/Edit/Delete operations
- Added breadcrumb navigation (Projects > Project Name > Epics)
- Included loading states with Skeletons
- Added error handling and user feedback with toast notifications
- Implemented responsive grid layout (mobile/tablet/desktop)
- Added hover effects and inline edit/delete actions
- Integrated with existing hooks (useEpics, useCreateEpic, useUpdateEpic, useDeleteEpic)
- Used shadcn/ui components (Card, Dialog, AlertDialog, Badge, Select)
- Added status and priority color coding
- Displayed estimated/actual hours and creation time
- Implemented empty state for projects with no epics

Technical details:
- Used react-hook-form with zod validation
- Implemented optimistic UI updates
- Followed existing patterns from Projects page
- Full TypeScript type safety

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

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

app/(dashboard)/projects/[id]/epics/page.tsx

@@ -0,0 +1,366 @@
+'use client';
+
+import { use, useState } from 'react';
+import Link from 'next/link';
+import { useRouter } from 'next/navigation';
+import {
+  ArrowLeft,
+  Plus,
+  Edit,
+  Trash2,
+  Loader2,
+  ListTodo,
+  Calendar,
+  Clock,
+} from 'lucide-react';
+import { Button } from '@/components/ui/button';
+import { Badge } from '@/components/ui/badge';
+import { Skeleton } from '@/components/ui/skeleton';
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardHeader,
+  CardTitle,
+} from '@/components/ui/card';
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog';
+import {
+  AlertDialog,
+  AlertDialogAction,
+  AlertDialogCancel,
+  AlertDialogContent,
+  AlertDialogDescription,
+  AlertDialogFooter,
+  AlertDialogHeader,
+  AlertDialogTitle,
+} from '@/components/ui/alert-dialog';
+import { useProject } from '@/lib/hooks/use-projects';
+import { useEpics, useDeleteEpic } from '@/lib/hooks/use-epics';
+import { EpicForm } from '@/components/epics/epic-form';
+import { formatDistanceToNow } from 'date-fns';
+import { toast } from 'sonner';
+import type { Epic, WorkItemStatus, WorkItemPriority } from '@/types/project';
+
+interface EpicsPageProps {
+  params: Promise<{ id: string }>;
+}
+
+export default function EpicsPage({ params }: EpicsPageProps) {
+  const { id: projectId } = use(params);
+  const router = useRouter();
+  const [isCreateDialogOpen, setIsCreateDialogOpen] = useState(false);
+  const [editingEpic, setEditingEpic] = useState<Epic | null>(null);
+  const [deletingEpicId, setDeletingEpicId] = useState<string | null>(null);
+
+  const { data: project, isLoading: projectLoading } = useProject(projectId);
+  const { data: epics, isLoading: epicsLoading, error } = useEpics(projectId);
+  const deleteEpic = useDeleteEpic();
+
+  const handleDelete = async () => {
+    if (!deletingEpicId) return;
+
+    try {
+      await deleteEpic.mutateAsync(deletingEpicId);
+      setDeletingEpicId(null);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : 'Failed to delete epic';
+      toast.error(message);
+    }
+  };
+
+  const getStatusColor = (status: WorkItemStatus) => {
+    switch (status) {
+      case 'Backlog':
+        return 'secondary';
+      case 'Todo':
+        return 'outline';
+      case 'InProgress':
+        return 'default';
+      case 'Done':
+        return 'success' as any;
+      default:
+        return 'secondary';
+    }
+  };
+
+  const getPriorityColor = (priority: WorkItemPriority) => {
+    switch (priority) {
+      case 'Low':
+        return 'bg-blue-100 text-blue-700 hover:bg-blue-100';
+      case 'Medium':
+        return 'bg-yellow-100 text-yellow-700 hover:bg-yellow-100';
+      case 'High':
+        return 'bg-orange-100 text-orange-700 hover:bg-orange-100';
+      case 'Critical':
+        return 'bg-red-100 text-red-700 hover:bg-red-100';
+      default:
+        return 'secondary';
+    }
+  };
+
+  if (projectLoading || epicsLoading) {
+    return (
+      <div className="space-y-6">
+        <Skeleton className="h-10 w-32" />
+        <div className="flex items-center justify-between">
+          <div className="space-y-2">
+            <Skeleton className="h-9 w-48" />
+            <Skeleton className="h-5 w-64" />
+          </div>
+          <Skeleton className="h-10 w-32" />
+        </div>
+        <div className="grid gap-4 md:grid-cols-2 lg:grid-cols-3">
+          {Array.from({ length: 6 }).map((_, i) => (
+            <Card key={i}>
+              <CardHeader>
+                <Skeleton className="h-6 w-3/4" />
+                <Skeleton className="h-4 w-1/2 mt-2" />
+              </CardHeader>
+              <CardContent>
+                <Skeleton className="h-16 w-full" />
+              </CardContent>
+            </Card>
+          ))}
+        </div>
+      </div>
+    );
+  }
+
+  if (error || !project) {
+    return (
+      <div className="flex items-center justify-center min-h-[400px]">
+        <Card className="w-full max-w-md">
+          <CardHeader>
+            <CardTitle className="text-destructive">Error Loading Epics</CardTitle>
+            <CardDescription>
+              {error instanceof Error ? error.message : 'Failed to load epics'}
+            </CardDescription>
+          </CardHeader>
+          <CardContent className="flex gap-2">
+            <Button onClick={() => router.back()}>Go Back</Button>
+            <Button onClick={() => window.location.reload()} variant="outline">
+              Retry
+            </Button>
+          </CardContent>
+        </Card>
+      </div>
+    );
+  }
+
+  return (
+    <div className="space-y-6">
+      {/* Breadcrumb */}
+      <div className="flex items-center gap-2 text-sm text-muted-foreground">
+        <Link href="/projects" className="hover:text-foreground">
+          Projects
+        </Link>
+        <span>/</span>
+        <Link href={`/projects/${projectId}`} className="hover:text-foreground">
+          {project.name}
+        </Link>
+        <span>/</span>
+        <span className="text-foreground">Epics</span>
+      </div>
+
+      {/* Header */}
+      <div className="flex items-start justify-between">
+        <div className="space-y-2">
+          <div className="flex items-center gap-3">
+            <Button variant="ghost" size="icon" asChild>
+              <Link href={`/projects/${projectId}`}>
+                <ArrowLeft className="h-5 w-5" />
+              </Link>
+            </Button>
+            <div>
+              <h1 className="text-3xl font-bold tracking-tight">Epics</h1>
+              <p className="text-muted-foreground mt-1">
+                Manage epics for {project.name}
+              </p>
+            </div>
+          </div>
+        </div>
+        <Button onClick={() => setIsCreateDialogOpen(true)}>
+          <Plus className="mr-2 h-4 w-4" />
+          New Epic
+        </Button>
+      </div>
+
+      {/* Epics Grid */}
+      {epics && epics.length > 0 ? (
+        <div className="grid gap-4 md:grid-cols-2 lg:grid-cols-3">
+          {epics.map((epic) => (
+            <Card
+              key={epic.id}
+              className="group transition-all hover:shadow-lg hover:border-primary relative"
+            >
+              <CardHeader>
+                <div className="flex items-start justify-between gap-2">
+                  <div className="space-y-2 flex-1">
+                    <Link
+                      href={`/epics/${epic.id}`}
+                      className="block hover:underline"
+                    >
+                      <CardTitle className="line-clamp-2 text-lg">
+                        {epic.title}
+                      </CardTitle>
+                    </Link>
+                    <div className="flex items-center gap-2 flex-wrap">
+                      <Badge variant={getStatusColor(epic.status)}>
+                        {epic.status}
+                      </Badge>
+                      <Badge className={getPriorityColor(epic.priority)}>
+                        {epic.priority}
+                      </Badge>
+                    </div>
+                  </div>
+                  <div className="flex gap-1 opacity-0 group-hover:opacity-100 transition-opacity">
+                    <Button
+                      variant="ghost"
+                      size="icon"
+                      className="h-8 w-8"
+                      onClick={(e) => {
+                        e.preventDefault();
+                        setEditingEpic(epic);
+                      }}
+                    >
+                      <Edit className="h-4 w-4" />
+                    </Button>
+                    <Button
+                      variant="ghost"
+                      size="icon"
+                      className="h-8 w-8 text-destructive hover:text-destructive"
+                      onClick={(e) => {
+                        e.preventDefault();
+                        setDeletingEpicId(epic.id);
+                      }}
+                    >
+                      <Trash2 className="h-4 w-4" />
+                    </Button>
+                  </div>
+                </div>
+              </CardHeader>
+              <CardContent className="space-y-4">
+                {epic.description ? (
+                  <p className="text-sm text-muted-foreground line-clamp-3">
+                    {epic.description}
+                  </p>
+                ) : (
+                  <p className="text-sm text-muted-foreground italic">
+                    No description
+                  </p>
+                )}
+                <div className="space-y-2 text-xs text-muted-foreground">
+                  {epic.estimatedHours && (
+                    <div className="flex items-center gap-1">
+                      <Clock className="h-3 w-3" />
+                      <span>Estimated: {epic.estimatedHours}h</span>
+                      {epic.actualHours && (
+                        <span className="ml-2">
+                          / Actual: {epic.actualHours}h
+                        </span>
+                      )}
+                    </div>
+                  )}
+                  <div className="flex items-center gap-1">
+                    <Calendar className="h-3 w-3" />
+                    <span>
+                      Created {formatDistanceToNow(new Date(epic.createdAt), { addSuffix: true })}
+                    </span>
+                  </div>
+                </div>
+              </CardContent>
+            </Card>
+          ))}
+        </div>
+      ) : (
+        <Card className="flex flex-col items-center justify-center py-16">
+          <ListTodo className="h-12 w-12 text-muted-foreground mb-4" />
+          <CardTitle className="mb-2">No epics yet</CardTitle>
+          <CardDescription className="mb-4 text-center max-w-md">
+            Get started by creating your first epic to organize major features and initiatives
+          </CardDescription>
+          <Button onClick={() => setIsCreateDialogOpen(true)}>
+            <Plus className="mr-2 h-4 w-4" />
+            Create Epic
+          </Button>
+        </Card>
+      )}
+
+      {/* Create Epic Dialog */}
+      <Dialog open={isCreateDialogOpen} onOpenChange={setIsCreateDialogOpen}>
+        <DialogContent className="max-w-2xl max-h-[90vh] overflow-y-auto">
+          <DialogHeader>
+            <DialogTitle>Create New Epic</DialogTitle>
+            <DialogDescription>
+              Add a new epic to organize major features and initiatives
+            </DialogDescription>
+          </DialogHeader>
+          <EpicForm
+            projectId={projectId}
+            onSuccess={() => setIsCreateDialogOpen(false)}
+            onCancel={() => setIsCreateDialogOpen(false)}
+          />
+        </DialogContent>
+      </Dialog>
+
+      {/* Edit Epic Dialog */}
+      <Dialog open={!!editingEpic} onOpenChange={() => setEditingEpic(null)}>
+        <DialogContent className="max-w-2xl max-h-[90vh] overflow-y-auto">
+          <DialogHeader>
+            <DialogTitle>Edit Epic</DialogTitle>
+            <DialogDescription>
+              Update the epic details
+            </DialogDescription>
+          </DialogHeader>
+          {editingEpic && (
+            <EpicForm
+              projectId={projectId}
+              epic={editingEpic}
+              onSuccess={() => setEditingEpic(null)}
+              onCancel={() => setEditingEpic(null)}
+            />
+          )}
+        </DialogContent>
+      </Dialog>
+
+      {/* Delete Confirmation Dialog */}
+      <AlertDialog
+        open={!!deletingEpicId}
+        onOpenChange={() => setDeletingEpicId(null)}
+      >
+        <AlertDialogContent>
+          <AlertDialogHeader>
+            <AlertDialogTitle>Are you sure?</AlertDialogTitle>
+            <AlertDialogDescription>
+              This action cannot be undone. This will permanently delete the epic
+              and all its associated stories and tasks.
+            </AlertDialogDescription>
+          </AlertDialogHeader>
+          <AlertDialogFooter>
+            <AlertDialogCancel>Cancel</AlertDialogCancel>
+            <AlertDialogAction
+              onClick={handleDelete}
+              className="bg-destructive text-destructive-foreground hover:bg-destructive/90"
+              disabled={deleteEpic.isPending}
+            >
+              {deleteEpic.isPending ? (
+                <>
+                  <Loader2 className="mr-2 h-4 w-4 animate-spin" />
+                  Deleting...
+                </>
+              ) : (
+                'Delete Epic'
+              )}
+            </AlertDialogAction>
+          </AlertDialogFooter>
+        </AlertDialogContent>
+      </AlertDialog>
+    </div>
+  );
+}