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/category.service.ts

@@ -0,0 +1,14 @@
+import api from "@/lib/api";
+import type { Category } from "@/types/content";
+
+export const CategoryService = {
+  async getAll(): Promise<Category[]> {
+    const { data } = await api.get<Category[]>("/categories");
+    return data;
+  },
+
+  async getOne(id: string): Promise<Category> {
+    const { data } = await api.get<Category>(`/categories/${id}`);
+    return data;
+  },
+};