feat(frontend): Implement Issue management and Kanban board

Add comprehensive Issue management functionality with drag-and-drop Kanban board.

Changes:
- Created Issue API client (issues.ts) with CRUD operations
- Implemented React Query hooks for Issue data management
- Added IssueCard component with drag-and-drop support using @dnd-kit
- Created KanbanColumn component with droppable zones
- Built CreateIssueDialog with form validation using zod
- Implemented Kanban page at /projects/[id]/kanban with DnD status changes
- Added missing UI components (textarea, select, skeleton)
- Enhanced API client with helper methods (get, post, put, patch, delete)
- Installed dependencies: @dnd-kit/core, @dnd-kit/sortable, @dnd-kit/utilities, @radix-ui/react-select, sonner
- Fixed SignalR ConnectionManager TypeScript error
- Preserved legacy KanbanBoard component for backward compatibility

Features:
- Drag and drop issues between Backlog, Todo, InProgress, and Done columns
- Real-time status updates via API
- Issue creation with type (Story, Task, Bug, Epic) and priority
- Visual feedback with priority colors and type icons
- Toast notifications for user actions

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

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

components/features/kanban/IssueCard.tsx

@@ -0,0 +1,58 @@
+'use client';
+
+import { useSortable } from '@dnd-kit/sortable';
+import { CSS } from '@dnd-kit/utilities';
+import { Card, CardContent } from '@/components/ui/card';
+import { Badge } from '@/components/ui/badge';
+import { Issue } from '@/lib/api/issues';
+
+interface IssueCardProps {
+  issue: Issue;
+}
+
+export function IssueCard({ issue }: IssueCardProps) {
+  const { attributes, listeners, setNodeRef, transform, transition } =
+    useSortable({ id: issue.id });
+
+  const style = {
+    transform: CSS.Transform.toString(transform),
+    transition,
+  };
+
+  const priorityColors = {
+    Low: 'bg-gray-100 text-gray-700',
+    Medium: 'bg-blue-100 text-blue-700',
+    High: 'bg-orange-100 text-orange-700',
+    Critical: 'bg-red-100 text-red-700',
+  };
+
+  const typeIcons = {
+    Story: '📖',
+    Task: '✓',
+    Bug: '🐛',
+    Epic: '🚀',
+  };
+
+  return (
+    <Card
+      ref={setNodeRef}
+      style={style}
+      {...attributes}
+      {...listeners}
+      className="cursor-grab active:cursor-grabbing hover:shadow-md transition-shadow"
+    >
+      <CardContent className="p-3 space-y-2">
+        <div className="flex items-start gap-2">
+          <span>{typeIcons[issue.type]}</span>
+          <h3 className="text-sm font-medium flex-1">{issue.title}</h3>
+        </div>
+        <div className="flex items-center gap-2">
+          <Badge variant="outline" className={priorityColors[issue.priority]}>
+            {issue.priority}
+          </Badge>
+          <Badge variant="secondary">{issue.type}</Badge>
+        </div>
+      </CardContent>
+    </Card>
+  );
+}