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/cjs/prepend.d.ts

@@ -0,0 +1,7 @@
+/**
+ * Insert a given element as the first child of a parent element.
+ *
+ * @param node the element to prepend
+ * @param parent the parent element
+ */
+export default function prepend(node: Element | null, parent: Element | null): Element | null;