feat: introduce new app routes with modular structure and enhanced features

Added modular app routes including `login`, `dashboard`, `categories`, `trends`, and `upload`. Introduced reusable components such as `ContentList`, `ContentSkeleton`, and `AppSidebar` for improved UI consistency. Enhanced authentication with `AuthProvider` and implemented lazy loading, dynamic layouts, and infinite scrolling for better performance.

frontend/src/services/favorite.service.ts

@@ -0,0 +1,17 @@
+import api from "@/lib/api";
+import type { Content, PaginatedResponse } from "@/types/content";
+
+export const FavoriteService = {
+  async add(contentId: string): Promise<void> {
+    await api.post(`/favorites/${contentId}`);
+  },
+
+  async remove(contentId: string): Promise<void> {
+    await api.delete(`/favorites/${contentId}`);
+  },
+
+  async list(params: { limit: number; offset: number }): Promise<PaginatedResponse<Content>> {
+    const { data } = await api.get<PaginatedResponse<Content>>("/favorites", { params });
+    return data;
+  },
+};