feat: implement structured grading system with predefined assessment types

- Add structured grading policy with predefined types (Continuous Assessment, Midterm, Final Test, Exam)
- Replace free-text category input with combobox selection in Grading Policy page
- Update Lesson Editor to use dropdown selector for grading category assignment
- Fix create_grading_category handler to capture organization context
- Fix update_course handler to set audit context in database transaction
- Implement getImageUrl helper for proper asset path resolution
- Add unoptimized prop to organization logo images to bypass Next.js optimization
- Add database migrations for organization_id in content tables
- Seed default tutorial courses for Admin, Instructor, and Student roles
- Fix audit log constraints and content schema issues

web/studio/src/components/AuthGuard.tsx

@@ -0,0 +1,37 @@
+"use client";
+
+import { useAuth } from "@/context/AuthContext";
+import { useRouter, usePathname } from "next/navigation";
+import { useEffect } from "react";
+
+export default function AuthGuard({ children }: { children: React.ReactNode }) {
+    const { user, loading } = useAuth();
+    const router = useRouter();
+    const pathname = usePathname();
+
+    useEffect(() => {
+        if (!loading) {
+            const isAuthPage = pathname?.startsWith("/auth");
+            if (!user && !isAuthPage) {
+                router.push("/auth/login");
+            } else if (user && isAuthPage) {
+                router.push("/");
+            }
+        }
+    }, [user, loading, pathname, router]);
+
+    if (loading) {
+        return (
+            <div className="min-h-screen bg-gray-950 flex items-center justify-center">
+                <div className="w-12 h-12 border-4 border-blue-500/20 border-t-blue-500 rounded-full animate-spin"></div>
+            </div>
+        );
+    }
+
+    const isAuthPage = pathname?.startsWith("/auth");
+    if (!user && !isAuthPage) {
+        return null; // Prevents flashing protected content
+    }
+
+    return <>{children}</>;
+}