feat : add task management with kanban and backlog

Add kanban board with drag-and-drop, backlog section, task/group
drawers, DTOs, services, and i18n translations.

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

frontend/services/task-efforts.ts

@@ -0,0 +1,32 @@
+import type { TaskEffort, TaskEffortWrite } from './dto/task-effort'
+import type { HydraCollection } from '~/utils/api'
+import { extractHydraMembers } from '~/utils/api'
+
+export function useTaskEffortService() {
+    const api = useApi()
+
+    async function getAll(): Promise<TaskEffort[]> {
+        const data = await api.get<HydraCollection<TaskEffort>>('/task_efforts')
+        return extractHydraMembers(data)
+    }
+
+    async function create(payload: TaskEffortWrite): Promise<TaskEffort> {
+        return api.post<TaskEffort>('/task_efforts', payload as Record<string, unknown>, {
+            toastSuccessKey: 'taskEfforts.created',
+        })
+    }
+
+    async function update(id: number, payload: Partial<TaskEffortWrite>): Promise<TaskEffort> {
+        return api.patch<TaskEffort>(`/task_efforts/${id}`, payload as Record<string, unknown>, {
+            toastSuccessKey: 'taskEfforts.updated',
+        })
+    }
+
+    async function remove(id: number): Promise<void> {
+        await api.delete(`/task_efforts/${id}`, {}, {
+            toastSuccessKey: 'taskEfforts.deleted',
+        })
+    }
+
+    return { getAll, create, update, remove }
+}