feat(exam): Assessment dashboard + /exam-marker route; remove old CCExamMarker (S4-8)

- New examRepository (R2.1 seam): the only module talking to /api/exam (Supabase
  JWT → Bearer, axios to API_BASE). list/get/create/archive templates.
- ExamDashboardPage (/exam-marker): lists institute templates, create dialog,
  archive; cards link to setup (S4-9). Wrapped in ErrorBoundary (R6.4).
- exam.types.ts mirrors the API contract.
- Dashboard 'Exam Marker' quick action (top-level discovery, R1.3/R6.1).
  Note: the in-canvas TeacherNavigation is unsuitable for a nav section (it's
  the worker prev/next tab bar) — flagged; used the dashboard entry instead.
- R1.1 removal: deleted src/pages/tldraw/CCExamMarker/ (old 3-PDF viewer) and
  the now-dead CCExamMarkerPanel + its wiring in CCPanel/BasePanel (examMarkerProps
  was only ever passed by the deleted page).
- Fixed pre-existing broken AppRoutes test (missing TimetableListPage mock export).

Build green (vite); AppRoutes route tests pass; typecheck clean for new files.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

.gitignore

@@ -47,3 +47,6 @@ docker-compose.override.yml
 # Local environment variants
 .env.dev
 .env.prod
+
+# Playwright test artifacts
+test-results/