feat(ST-1114): add shared Markdown wrapper, apply to task-detail and story-dialog

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/backlog/story-dialog.tsx

@@ -1,6 +1,7 @@
 'use client'
 
 import { useEffect, useRef, useState, useTransition } from 'react'
+import { Markdown } from '@/components/markdown'
 import { useActionState } from 'react'
 import { useFormStatus } from 'react-dom'
 import { toast } from 'sonner'
@@ -231,7 +232,7 @@ export function StoryDialog({ state, onClose, isDemo = false }: StoryDialogProps
                 {story?.description && (
                   <div>
                     <p className="text-xs font-medium text-muted-foreground uppercase tracking-wide mb-1">Omschrijving</p>
-                    <p className="text-sm">{story.description}</p>
+                    <Markdown>{story.description}</Markdown>
                   </div>
                 )}
                 {story?.acceptance_criteria && (