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/api/client.ts

@@ -133,3 +133,31 @@ apiClient.interceptors.response.use(
     return Promise.reject(error);
   }
 );
+
+// API helper functions
+export const api = {
+  get: async <T>(url: string, config?: any): Promise<T> => {
+    const response = await apiClient.get(url, config);
+    return response.data;
+  },
+
+  post: async <T>(url: string, data?: any, config?: any): Promise<T> => {
+    const response = await apiClient.post(url, data, config);
+    return response.data;
+  },
+
+  put: async <T>(url: string, data?: any, config?: any): Promise<T> => {
+    const response = await apiClient.put(url, data, config);
+    return response.data;
+  },
+
+  patch: async <T>(url: string, data?: any, config?: any): Promise<T> => {
+    const response = await apiClient.patch(url, data, config);
+    return response.data;
+  },
+
+  delete: async <T>(url: string, config?: any): Promise<T> => {
+    const response = await apiClient.delete(url, config);
+    return response.data;
+  },
+};