feat: inject ContentsRepository into CommentsService for better integration

- Added `ContentsRepository` as a dependency to `CommentsService` and updated tests for mock setup.
- Adjusted import order in relevant files to align with project standards.

backend/src/comments/comments.service.spec.ts

@@ -1,5 +1,6 @@
 import { ForbiddenException, NotFoundException } from "@nestjs/common";
 import { Test, TestingModule } from "@nestjs/testing";
+import { ContentsRepository } from "../contents/repositories/contents.repository";
 import { EventsGateway } from "../realtime/events.gateway";
 import { S3Service } from "../s3/s3.service";
 import { CommentsService } from "./comments.service";
@@ -25,12 +26,17 @@ describe("CommentsService", () => {
 		isLikedByUser: jest.fn(),
 	};
 
+	const mockContentsRepository = {
+		findOne: jest.fn(),
+	};
+
 	const mockS3Service = {
 		getPublicUrl: jest.fn(),
 	};
 
 	const mockEventsGateway = {
 		sendToContent: jest.fn(),
+		sendToUser: jest.fn(),
 	};
 
 	beforeEach(async () => {
@@ -40,6 +46,7 @@ describe("CommentsService", () => {
 				CommentsService,
 				{ provide: CommentsRepository, useValue: mockCommentsRepository },
 				{ provide: CommentLikesRepository, useValue: mockCommentLikesRepository },
+				{ provide: ContentsRepository, useValue: mockContentsRepository },
 				{ provide: S3Service, useValue: mockS3Service },
 				{ provide: EventsGateway, useValue: mockEventsGateway },
 			],