feat: home page with MUI components

- Rewrote frontend from JSX to TypeScript (TSX)
- AppLayout with MUI AppBar, ThemeProvider, CssBaseline
- HomePage at / with dashboard metrics and recent updates
- MetricsPanel with 4 metric cards (total, interviews, offers, rejection rate)
- UpdateCard for each job update with status chip
- LoadingSkeleton during data fetch
- Error Alert on API failure
- Create New Job Application button navigating to /applications/new
- Vite proxy for /api → backend on :8000
- useDashboardData custom hook with concurrent fetch

Closes #2

api/jobs/urls.py

@@ -0,0 +1,12 @@
+from django.urls import include, path
+from rest_framework.routers import DefaultRouter
+
+from . import views
+
+router = DefaultRouter()
+router.register(r"applications", views.JobApplicationViewSet, basename="job-application")
+router.register(r"updates", views.JobUpdateViewSet, basename="job-update")
+
+urlpatterns = [
+    path("", include(router.urls)),
+]