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/providers/auth-provider.tsx

@@ -0,0 +1,99 @@
+"use client";
+
+import * as React from "react";
+import { UserService } from "@/services/user.service";
+import { AuthService } from "@/services/auth.service";
+import type { User } from "@/types/user";
+import { useRouter } from "next/navigation";
+import { toast } from "sonner";
+
+interface AuthContextType {
+  user: User | null;
+  isLoading: boolean;
+  isAuthenticated: boolean;
+  login: (email: string, password: string) => Promise<void>;
+  register: (payload: any) => Promise<void>;
+  logout: () => Promise<void>;
+  refreshUser: () => Promise<void>;
+}
+
+const AuthContext = React.createContext<AuthContextType | null>(null);
+
+export function AuthProvider({ children }: { children: React.ReactNode }) {
+  const [user, setUser] = React.useState<User | null>(null);
+  const [isLoading, setIsLoading] = React.useState(true);
+  const router = useRouter();
+
+  const refreshUser = React.useCallback(async () => {
+    try {
+      const userData = await UserService.getMe();
+      setUser(userData);
+    } catch (error) {
+      setUser(null);
+    } finally {
+      setIsLoading(false);
+    }
+  }, []);
+
+  React.useEffect(() => {
+    refreshUser();
+  }, [refreshUser]);
+
+  const login = async (email: string, password: string) => {
+    try {
+      await AuthService.login(email, password);
+      await refreshUser();
+      toast.success("Connexion réussie !");
+      router.push("/");
+    } catch (error: any) {
+      toast.error(error.response?.data?.message || "Erreur de connexion");
+      throw error;
+    }
+  };
+
+  const register = async (payload: any) => {
+    try {
+      await AuthService.register(payload);
+      toast.success("Inscription réussie ! Vous pouvez maintenant vous connecter.");
+      router.push("/login");
+    } catch (error: any) {
+      toast.error(error.response?.data?.message || "Erreur d'inscription");
+      throw error;
+    }
+  };
+
+  const logout = async () => {
+    try {
+      await AuthService.logout();
+      setUser(null);
+      toast.success("Déconnexion réussie");
+      router.push("/");
+    } catch (error) {
+      toast.error("Erreur lors de la déconnexion");
+    }
+  };
+
+  return (
+    <AuthContext.Provider
+      value={{
+        user,
+        isLoading,
+        isAuthenticated: !!user,
+        login,
+        register,
+        logout,
+        refreshUser,
+      }}
+    >
+      {children}
+    </AuthContext.Provider>
+  );
+}
+
+export const useAuth = () => {
+  const context = React.useContext(AuthContext);
+  if (!context) {
+    throw new Error("useAuth must be used within an AuthProvider");
+  }
+  return context;
+};