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/app/(dashboard)/_hooks/use-infinite-scroll.ts

@@ -0,0 +1,42 @@
+import * as React from "react";
+
+interface UseInfiniteScrollOptions {
+  threshold?: number;
+  hasMore: boolean;
+  loading: boolean;
+  onLoadMore: () => void;
+}
+
+export function useInfiniteScroll({
+  threshold = 1.0,
+  hasMore,
+  loading,
+  onLoadMore,
+}: UseInfiniteScrollOptions) {
+  const loaderRef = React.useRef<HTMLDivElement>(null);
+
+  React.useEffect(() => {
+    const observer = new IntersectionObserver(
+      (entries) => {
+        if (entries[0].isIntersecting && hasMore && !loading) {
+          onLoadMore();
+        }
+      },
+      { threshold }
+    );
+
+    const currentLoader = loaderRef.current;
+    if (currentLoader) {
+      observer.observe(currentLoader);
+    }
+
+    return () => {
+      if (currentLoader) {
+        observer.unobserve(currentLoader);
+      }
+      observer.disconnect();
+    };
+  }, [onLoadMore, hasMore, loading, threshold]);
+
+  return { loaderRef };
+}