feat: Enrich DTOs and UI to display member names instead of UUIDs for task assignees, creators, and shift signups.

frontend/src/hooks/useShifts.ts

@@ -38,6 +38,7 @@ export interface ShiftDetailDto {
 export interface ShiftSignupDto {
   id: string;
   memberId: string;
+  memberName?: string;
   externalUserId?: string;
   signedUpAt: string;
 }

frontend/src/hooks/useTasks.ts

@@ -14,6 +14,7 @@ export interface TaskListItemDto {
   title: string;
   status: string;
   assigneeId: string | null;
+  assigneeName?: string;
   createdAt: string;
   isAssignedToMe: boolean;
 }
@@ -24,7 +25,9 @@ export interface TaskDetailDto {
   description: string | null;
   status: string;
   assigneeId: string | null;
+  assigneeName?: string;
   createdById: string;
+  createdByName?: string;
   clubId: string;
   dueDate: string | null;
   createdAt: string;