fix: scope instructor chat threads to the selected course

src/lib/chat.ts

@@ -49,8 +49,9 @@ type ChatThreadsPayload = {
   data?: unknown[];
 };
 
-export async function listInstructorChatThreads(accessToken: string, week?: number): Promise<InstructorChatThread[]> {
+export async function listInstructorChatThreads(accessToken: string, courseId: string, week?: number): Promise<InstructorChatThread[]> {
   const params = new URLSearchParams();
+  if (courseId) params.set('courseId', courseId);
   if (week) params.set('week', String(week));
   const queryString = params.toString();