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/dom-helpers/esm/ownerDocument.js

@@ -0,0 +1,8 @@
+/**
+ * Returns the owner document of a given element.
+ * 
+ * @param node the element
+ */
+export default function ownerDocument(node) {
+  return node && node.ownerDocument || document;
+}