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/KanbanBoard.tsx

@@ -1,12 +1,14 @@
 'use client';
 
-import { KanbanColumn } from './KanbanColumn';
+import { TaskCard } from './TaskCard';
 import type { KanbanBoard as KanbanBoardType } from '@/types/kanban';
 
 interface KanbanBoardProps {
   board: KanbanBoardType;
 }
 
+// Legacy KanbanBoard component using old Kanban type
+// For new Issue-based Kanban, use the page at /projects/[id]/kanban
 export function KanbanBoard({ board }: KanbanBoardProps) {
   return (
     <div className="space-y-4">
@@ -18,7 +20,27 @@ export function KanbanBoard({ board }: KanbanBoardProps) {
       </div>
       <div className="flex gap-4 overflow-x-auto pb-4">
         {board.columns.map((column) => (
-          <KanbanColumn key={column.status} column={column} />
+          <div
+            key={column.status}
+            className="flex min-w-[300px] flex-col rounded-lg border-2 bg-muted/50 p-4"
+          >
+            <div className="mb-4 flex items-center justify-between">
+              <h3 className="font-semibold">{column.title}</h3>
+              <span className="rounded-full bg-background px-2 py-0.5 text-xs font-medium">
+                {column.tasks.length}
+              </span>
+            </div>
+            <div className="flex-1 space-y-3">
+              {column.tasks.map((task) => (
+                <TaskCard key={task.id} task={task} />
+              ))}
+              {column.tasks.length === 0 && (
+                <div className="flex h-32 items-center justify-center rounded-lg border-2 border-dashed border-muted-foreground/25">
+                  <p className="text-sm text-muted-foreground">No tasks</p>
+                </div>
+              )}
+            </div>
+          </div>
         ))}
       </div>
       <p className="text-xs text-muted-foreground">