feat: add comment replies and liking functionality

- Introduced support for nested comment replies in both frontend and backend.
- Added comment liking and unliking features, including like count and "isLiked" state tracking.
- Updated database schema with `parentId` and new `comment_likes` table.
- Enhanced UI for threaded comments and implemented display of like counts and reply actions.
- Refactored APIs and repositories to support replies, likes, and enriched comment data.

backend/src/comments/repositories/comment-likes.repository.ts

@@ -0,0 +1,42 @@
+import { Injectable } from "@nestjs/common";
+import { and, eq, sql } from "drizzle-orm";
+import { DatabaseService } from "../../database/database.service";
+import { commentLikes } from "../../database/schemas/comment_likes";
+
+@Injectable()
+export class CommentLikesRepository {
+	constructor(private readonly databaseService: DatabaseService) {}
+
+	async addLike(commentId: string, userId: string) {
+		await this.databaseService.db
+			.insert(commentLikes)
+			.values({ commentId, userId })
+			.onConflictDoNothing();
+	}
+
+	async removeLike(commentId: string, userId: string) {
+		await this.databaseService.db
+			.delete(commentLikes)
+			.where(
+				and(eq(commentLikes.commentId, commentId), eq(commentLikes.userId, userId)),
+			);
+	}
+
+	async countByCommentId(commentId: string) {
+		const results = await this.databaseService.db
+			.select({ count: sql<number>`count(*)` })
+			.from(commentLikes)
+			.where(eq(commentLikes.commentId, commentId));
+		return Number(results[0]?.count || 0);
+	}
+
+	async isLikedByUser(commentId: string, userId: string) {
+		const results = await this.databaseService.db
+			.select()
+			.from(commentLikes)
+			.where(
+				and(eq(commentLikes.commentId, commentId), eq(commentLikes.userId, userId)),
+			);
+		return !!results[0];
+	}
+}