feat(ui): add task management UI with list, detail, and create pages

Implements Task 19: Task List + Task Detail + Status Transitions UI

New components:
- useTasks hook: TanStack Query hooks (useTasks, useTask, useCreateTask, useUpdateTask)
- Task list page: shadcn Table with status filter, pagination, status badges
- Task detail page: Full task info with valid status transition buttons
- New task form: Create task with title, description, assigneeId, dueDate

Key features:
- Status transitions match backend logic: Open→Assigned→InProgress→Review→Done
- Review status allows back-transition to InProgress (only bidirectional)
- Only valid next states shown as buttons (VALID_TRANSITIONS map)
- Status badge colors: Open=gray, Assigned=blue, InProgress=yellow, Review=red, Done=green
- TanStack Query with automatic cache invalidation on mutations
- Next.js 15+ async params pattern (use() hook)

TDD:
- 3 task list tests (renders rows, status badges, new task button)
- 3 task detail tests (Open→Assigned, InProgress→Review, Review→Done+InProgress)

All tests pass (31/31). Build succeeds.

frontend/src/hooks/useTasks.ts

@@ -0,0 +1,122 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { useTenant } from '@/contexts/tenant-context';
+import { apiClient } from '@/lib/api';
+
+export interface TaskListDto {
+  items: TaskListItemDto[];
+  total: number;
+  page: number;
+  pageSize: number;
+}
+
+export interface TaskListItemDto {
+  id: string;
+  title: string;
+  status: string;
+  assigneeId: string | null;
+  createdAt: string;
+}
+
+export interface TaskDetailDto {
+  id: string;
+  title: string;
+  description: string | null;
+  status: string;
+  assigneeId: string | null;
+  createdById: string;
+  clubId: string;
+  dueDate: string | null;
+  createdAt: string;
+  updatedAt: string;
+}
+
+export interface CreateTaskRequest {
+  title: string;
+  description?: string;
+  clubId: string;
+  assigneeId?: string;
+  dueDate?: string;
+}
+
+export interface UpdateTaskRequest {
+  title?: string;
+  description?: string;
+  status?: string;
+  assigneeId?: string;
+  dueDate?: string;
+}
+
+export function useTasks(filters?: { status?: string; page?: number }) {
+  const { activeClubId } = useTenant();
+
+  return useQuery<TaskListDto>({
+    queryKey: ['tasks', activeClubId, filters],
+    queryFn: async () => {
+      const params = new URLSearchParams();
+      if (filters?.status) params.append('status', filters.status);
+      if (filters?.page) params.append('page', filters.page.toString());
+      
+      const res = await apiClient(`/api/tasks?${params}`);
+      if (!res.ok) throw new Error('Failed to fetch tasks');
+      return res.json();
+    },
+    enabled: !!activeClubId,
+  });
+}
+
+export function useTask(id: string) {
+  const { activeClubId } = useTenant();
+
+  return useQuery<TaskDetailDto>({
+    queryKey: ['tasks', activeClubId, id],
+    queryFn: async () => {
+      const res = await apiClient(`/api/tasks/${id}`);
+      if (!res.ok) throw new Error('Failed to fetch task');
+      return res.json();
+    },
+    enabled: !!activeClubId && !!id,
+  });
+}
+
+export function useCreateTask() {
+  const queryClient = useQueryClient();
+  const { activeClubId } = useTenant();
+  
+  return useMutation({
+    mutationFn: async (data: Omit<CreateTaskRequest, 'clubId'>) => {
+      const payload: CreateTaskRequest = {
+        ...data,
+        clubId: activeClubId!,
+      };
+      const res = await apiClient('/api/tasks', {
+        method: 'POST',
+        body: JSON.stringify(payload),
+      });
+      if (!res.ok) throw new Error('Failed to create task');
+      return res.json();
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['tasks', activeClubId] });
+    },
+  });
+}
+
+export function useUpdateTask() {
+  const queryClient = useQueryClient();
+  const { activeClubId } = useTenant();
+  
+  return useMutation({
+    mutationFn: async ({ id, data }: { id: string; data: UpdateTaskRequest }) => {
+      const res = await apiClient(`/api/tasks/${id}`, {
+        method: 'PATCH',
+        body: JSON.stringify(data),
+      });
+      if (!res.ok) throw new Error('Failed to update task');
+      return res.json();
+    },
+    onSuccess: (_, variables) => {
+      queryClient.invalidateQueries({ queryKey: ['tasks', activeClubId] });
+      queryClient.invalidateQueries({ queryKey: ['tasks', activeClubId, variables.id] });
+    },
+  });
+}