feat(frontend): Refactor Kanban board to focus on Story management

Refactored the Kanban board from a mixed Epic/Story/Task view to focus exclusively on Stories, which are the right granularity for Kanban management.

Changes:
- Created StoryCard component with Epic breadcrumb, priority badges, and estimated hours display
- Updated KanbanColumn to use Story type and display epic names
- Created CreateStoryDialog for story creation with epic selection
- Added useProjectStories hook to fetch all stories across epics for a project
- Refactored Kanban page to show Stories only with drag-and-drop status updates
- Updated SignalR event handlers to focus on Story events only
- Changed UI text from 'New Issue' to 'New Story' and 'update issue status' to 'update story status'
- Implemented story status change via useChangeStoryStatus hook

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

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

components/features/kanban/KanbanColumn.tsx

@@ -3,16 +3,18 @@
 import { useDroppable } from '@dnd-kit/core';
 import { SortableContext, verticalListSortingStrategy } from '@dnd-kit/sortable';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
-import { Issue } from '@/lib/api/issues';
-import { IssueCard } from './IssueCard';
+import { Story } from '@/types/project';
+import { StoryCard } from './StoryCard';
 
 interface KanbanColumnProps {
   id: string;
   title: string;
-  issues: Issue[];
+  stories: Story[];
+  epicNames?: Record<string, string>; // Map of epicId -> epicName
+  taskCounts?: Record<string, number>; // Map of storyId -> taskCount
 }
 
-export function KanbanColumn({ id, title, issues }: KanbanColumnProps) {
+export function KanbanColumn({ id, title, stories, epicNames = {}, taskCounts = {} }: KanbanColumnProps) {
   const { setNodeRef } = useDroppable({ id });
 
   return (
@@ -20,21 +22,26 @@ export function KanbanColumn({ id, title, issues }: KanbanColumnProps) {
       <CardHeader className="pb-3">
         <CardTitle className="text-sm font-medium flex items-center justify-between">
           <span>{title}</span>
-          <span className="text-muted-foreground">{issues.length}</span>
+          <span className="text-muted-foreground">{stories.length}</span>
         </CardTitle>
       </CardHeader>
       <CardContent ref={setNodeRef} className="space-y-2 min-h-[400px]">
         <SortableContext
-          items={issues.map((i) => i.id)}
+          items={stories.map((s) => s.id)}
           strategy={verticalListSortingStrategy}
         >
-          {issues.map((issue) => (
-            <IssueCard key={issue.id} issue={issue} />
+          {stories.map((story) => (
+            <StoryCard
+              key={story.id}
+              story={story}
+              epicName={epicNames[story.epicId]}
+              taskCount={taskCounts[story.id]}
+            />
           ))}
         </SortableContext>
-        {issues.length === 0 && (
+        {stories.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 issues</p>
+            <p className="text-sm text-muted-foreground">No stories</p>
           </div>
         )}
       </CardContent>