fix(api): add clearAllMocks and explicit return type to GroupsModule

- Add jest.clearAllMocks() in beforeEach of both spec files to prevent
  call-history state from leaking between tests as the suites grow
- Define GroupSummary interface and use it as explicit return type for
  GroupsService.list() to satisfy TypeScript strict typing requirements

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

apps/api/src/modules/groups/groups.controller.spec.ts

@@ -10,6 +10,10 @@ const mockService = { list: jest.fn().mockResolvedValue(mockGroups) };
 describe('GroupsController', () => {
   let controller: GroupsController;
 
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
   beforeEach(async () => {
     const module: TestingModule = await Test.createTestingModule({
       controllers: [GroupsController],

apps/api/src/modules/groups/groups.service.spec.ts

@@ -11,6 +11,10 @@ describe('GroupsService', () => {
   let service: GroupsService;
   const mockPrisma = { group: { findMany: jest.fn().mockResolvedValue(mockGroups) } };
 
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
   beforeEach(async () => {
     const module: TestingModule = await Test.createTestingModule({
       providers: [

apps/api/src/modules/groups/groups.service.ts

@@ -1,11 +1,20 @@
 import { Injectable } from '@nestjs/common';
 import { PrismaService } from '../../prisma/prisma.service';
 
+interface GroupSummary {
+  id: string;
+  name: string;
+  platform: string;
+  platformId: string;
+  isActive: boolean;
+  accountId: string | null;
+}
+
 @Injectable()
 export class GroupsService {
   constructor(private readonly prisma: PrismaService) {}
 
-  list() {
+  list(): Promise<GroupSummary[]> {
     return this.prisma.group.findMany({
       orderBy: { name: 'asc' },
       select: { id: true, name: true, platform: true, platformId: true, isActive: true, accountId: true },