improvement: task assignment flow added. cases and tasks feature updated accordingly.

frontend/src/lib/api/cases.ts

@@ -1,6 +1,7 @@
 import { apiClient } from './client';
 import type {
   CasesFilterOptions,
+  AssignableTaskStaff,
   LabCaseDetail,
   ListLabCasesParams,
   PaginatedLabCases,
@@ -24,6 +25,22 @@ export const casesApi = {
     return response.data;
   },
 
+  listAssignableStaff: async (): Promise<{ success: boolean; data: AssignableTaskStaff[] }> => {
+    const response = await apiClient.get('/cases/assignable-staff');
+    return response.data;
+  },
+
+  assignTask: async (
+    caseId: string,
+    taskId: string,
+    assigneeUserId: string | null,
+  ): Promise<{ success: boolean; data: LabCaseDetail }> => {
+    const response = await apiClient.patch(`/cases/${caseId}/tasks/${taskId}/assign`, {
+      assigneeUserId,
+    });
+    return response.data;
+  },
+
   setCaseImportant: async (
     caseId: string,
     isImportant: boolean,