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/use-callback-ref/dist/es5/index.d.ts

@@ -0,0 +1,8 @@
+export { assignRef } from './assignRef';
+export { useCallbackRef } from './useRef';
+export { createCallbackRef } from './createRef';
+export { mergeRefs } from './mergeRef';
+export { useMergeRefs } from './useMergeRef';
+export { useTransformRef } from './useTransformRef';
+export { transformRef } from './transformRef';
+export { refToCallback, useRefToCallback } from './refToCallback';