feat: redesign Exams List page to show submitted custom exams

- Added Custom Exams tab showing all exams from Generation page
- Displays title, module badges, duration, and status
- Added Create Exam button
- Kept Exam Sessions tab for institutional sessions
- Search filters across exams

Made-with: Cursor

node_modules/@radix-ui/react-presence/dist/index.d.ts

@@ -0,0 +1,12 @@
+import * as React from 'react';
+
+interface PresenceProps {
+    children: React.ReactElement | ((props: {
+        present: boolean;
+    }) => React.ReactElement);
+    present: boolean;
+}
+declare const Presence: React.FC<PresenceProps>;
+declare const Root: React.FC<PresenceProps>;
+
+export { Presence, type PresenceProps, Root };