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>

lib/hooks/use-issues.ts

@@ -0,0 +1,102 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { issuesApi, Issue, CreateIssueDto, UpdateIssueDto } from '@/lib/api/issues';
+import { toast } from 'sonner';
+
+export function useIssues(projectId: string, status?: string) {
+  return useQuery({
+    queryKey: ['issues', projectId, status],
+    queryFn: () => issuesApi.list(projectId, status),
+    enabled: !!projectId,
+  });
+}
+
+export function useIssue(projectId: string, issueId: string) {
+  return useQuery({
+    queryKey: ['issue', projectId, issueId],
+    queryFn: () => issuesApi.getById(projectId, issueId),
+    enabled: !!projectId && !!issueId,
+  });
+}
+
+export function useCreateIssue(projectId: string) {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: (data: CreateIssueDto) => issuesApi.create(projectId, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['issues', projectId] });
+      toast.success('Issue created successfully');
+    },
+    onError: () => {
+      toast.error('Failed to create issue');
+    },
+  });
+}
+
+export function useUpdateIssue(projectId: string, issueId: string) {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: (data: UpdateIssueDto) =>
+      issuesApi.update(projectId, issueId, data),
+    onSuccess: (updatedIssue) => {
+      queryClient.setQueryData(['issue', projectId, issueId], updatedIssue);
+      queryClient.invalidateQueries({ queryKey: ['issues', projectId] });
+      toast.success('Issue updated successfully');
+    },
+    onError: () => {
+      toast.error('Failed to update issue');
+    },
+  });
+}
+
+export function useChangeIssueStatus(projectId: string) {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: ({ issueId, status }: { issueId: string; status: string }) =>
+      issuesApi.changeStatus(projectId, issueId, status),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['issues', projectId] });
+    },
+    onError: () => {
+      toast.error('Failed to change issue status');
+    },
+  });
+}
+
+export function useAssignIssue(projectId: string) {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: ({
+      issueId,
+      assigneeId,
+    }: {
+      issueId: string;
+      assigneeId: string | null;
+    }) => issuesApi.assign(projectId, issueId, assigneeId),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['issues', projectId] });
+      toast.success('Issue assigned successfully');
+    },
+    onError: () => {
+      toast.error('Failed to assign issue');
+    },
+  });
+}
+
+export function useDeleteIssue(projectId: string) {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: (issueId: string) => issuesApi.delete(projectId, issueId),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['issues', projectId] });
+      toast.success('Issue deleted successfully');
+    },
+    onError: () => {
+      toast.error('Failed to delete issue');
+    },
+  });
+}