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

web/vite.config.js

@@ -9,5 +9,11 @@ export default defineConfig({
     watch: {
       usePolling: true,
     },
+    proxy: {
+      "/api": {
+        target: "http://localhost:8000",
+        changeOrigin: true,
+      },
+    },
   },
 });