feat(codes): UI toont en accepteert code voor taken

- TaskDialog: code-input boven titel (font-mono, optional,
  placeholder "auto"), CodeBadge in dialog header bij edit
- EditTaskLoader: select code uit DB voor de dialog
- Solo page: vervang inline deriveTaskCode-logica door directe
  task.code uit DB
- Sprint page + TaskList + SprintBoardClient: Task-type krijgt
  verplicht code-veld; TaskList laat ongebruikte storyCode prop
  vallen omdat code-derivatie niet meer nodig is

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

components/sprint/task-list.tsx

@@ -17,7 +17,6 @@ import { Badge } from '@/components/ui/badge'
 import { CodeBadge } from '@/components/shared/code-badge'
 import { PanelNavBar } from '@/components/shared/panel-nav-bar'
 import { PRIORITY_BORDER } from '@/components/backlog/backlog-card'
-import { deriveTaskCode } from '@/lib/code'
 import { useSprintStore } from '@/stores/sprint-store'
 import { updateTaskStatusAction, reorderTasksAction } from '@/actions/tasks'
 import { DemoTooltip } from '@/components/shared/demo-tooltip'
@@ -38,6 +37,7 @@ const STATUS_LABELS: Record<string, string> = { TO_DO: 'To Do', IN_PROGRESS: 'Be
 
 export interface Task {
   id: string
+  code: string
   title: string
   description: string | null
   priority: number
@@ -48,7 +48,6 @@ export interface Task {
 
 interface TaskListProps {
   storyId: string
-  storyCode: string | null
   sprintId: string
   productId: string
   tasks: Task[]
@@ -126,7 +125,7 @@ function SortableTaskRow({
   )
 }
 
-export function TaskList({ storyId, storyCode, sprintId: _sprintId, productId: _productId, tasks, isDemo }: TaskListProps) {
+export function TaskList({ storyId, sprintId: _sprintId, productId: _productId, tasks, isDemo }: TaskListProps) {
   const { taskOrder, initTasks, reorderTasks, rollbackTasks } = useSprintStore()
   const [activeDragId, setActiveDragId] = useState<string | null>(null)
   const [, startTransition] = useTransition()
@@ -222,11 +221,11 @@ export function TaskList({ storyId, storyCode, sprintId: _sprintId, productId: _
             onDragEnd={handleDragEnd}
           >
             <SortableContext items={orderedTasks.map(t => t.id)} strategy={verticalListSortingStrategy}>
-              {orderedTasks.map((task, idx) => (
+              {orderedTasks.map((task) => (
                 <SortableTaskRow
                   key={task.id}
                   task={task}
-                  code={deriveTaskCode(storyCode, idx + 1)}
+                  code={task.code}
                   isDemo={isDemo}
                   onStatusToggle={() => handleStatusToggle(task)}
                   onEdit={() => openEditDialog(task.id)}