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/date-fns/_lib/defaultOptions.d.ts

@@ -0,0 +1,11 @@
+import type {
+  FirstWeekContainsDateOptions,
+  Locale,
+  LocalizedOptions,
+  WeekOptions,
+} from "../types.js";
+export type DefaultOptions = LocalizedOptions<keyof Locale> &
+  WeekOptions &
+  FirstWeekContainsDateOptions;
+export declare function getDefaultOptions(): DefaultOptions;
+export declare function setDefaultOptions(newOptions: DefaultOptions): void;