feat: add FavoritesModule with service, controller, and CRUD endpoints

Implemented FavoritesModule to manage user favorites. Includes service methods for adding, removing, and listing favorites, along with appropriate database integrations and API endpoints.

backend/src/favorites/favorites.controller.ts

@@ -0,0 +1,43 @@
+import {
+	Controller,
+	DefaultValuePipe,
+	Delete,
+	Get,
+	Param,
+	ParseIntPipe,
+	Post,
+	Query,
+	Req,
+	UseGuards,
+} from "@nestjs/common";
+import { AuthGuard } from "../auth/guards/auth.guard";
+import type { AuthenticatedRequest } from "../common/interfaces/request.interface";
+import { FavoritesService } from "./favorites.service";
+
+@UseGuards(AuthGuard)
+@Controller("favorites")
+export class FavoritesController {
+	constructor(private readonly favoritesService: FavoritesService) {}
+
+	@Post(":contentId")
+	add(@Req() req: AuthenticatedRequest, @Param("contentId") contentId: string) {
+		return this.favoritesService.addFavorite(req.user.sub, contentId);
+	}
+
+	@Delete(":contentId")
+	remove(
+		@Req() req: AuthenticatedRequest,
+		@Param("contentId") contentId: string,
+	) {
+		return this.favoritesService.removeFavorite(req.user.sub, contentId);
+	}
+
+	@Get()
+	list(
+		@Req() req: AuthenticatedRequest,
+		@Query("limit", new DefaultValuePipe(10), ParseIntPipe) limit: number,
+		@Query("offset", new DefaultValuePipe(0), ParseIntPipe) offset: number,
+	) {
+		return this.favoritesService.getUserFavorites(req.user.sub, limit, offset);
+	}
+}