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/closest.d.ts

@@ -0,0 +1,8 @@
+/**
+ * Returns the closest parent element that matches a given selector.
+ *
+ * @param node the reference element
+ * @param selector the selector to match
+ * @param stopAt stop traversing when this element is found
+ */
+export default function closest(node: Element, selector: string, stopAt?: Element): Element | null;