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>

package.json

@@ -10,11 +10,15 @@
     "format": "prettier --write \"**/*.{ts,tsx,js,jsx,json,css,md}\""
   },
   "dependencies": {
+    "@dnd-kit/core": "^6.3.1",
+    "@dnd-kit/sortable": "^10.0.0",
+    "@dnd-kit/utilities": "^3.2.2",
     "@hookform/resolvers": "^5.2.2",
     "@microsoft/signalr": "^9.0.6",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-dropdown-menu": "^2.1.16",
     "@radix-ui/react-label": "^2.1.7",
+    "@radix-ui/react-select": "^2.2.6",
     "@radix-ui/react-slot": "^1.2.3",
     "@tanstack/react-query": "^5.90.6",
     "@tanstack/react-query-devtools": "^5.90.2",
@@ -26,6 +30,7 @@
     "react": "19.2.0",
     "react-dom": "19.2.0",
     "react-hook-form": "^7.66.0",
+    "sonner": "^2.0.7",
     "tailwind-merge": "^3.3.1",
     "zod": "^4.1.12",
     "zustand": "^5.0.8"