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/src/hooks/useDashboardData.ts

@@ -0,0 +1,50 @@
+import { useState, useEffect, useCallback } from "react";
+import type { DashboardData, JobUpdate, DashboardMetrics } from "../types/index.ts";
+
+interface UseDashboardDataResult {
+  data: DashboardData | null;
+  loading: boolean;
+  error: string | null;
+  refetch: () => void;
+}
+
+const API_BASE = "/api";
+
+async function fetchJson<T>(url: string): Promise<T> {
+  const response = await fetch(url);
+  if (!response.ok) {
+    throw new Error(`HTTP ${response.status}: ${response.statusText}`);
+  }
+  return response.json() as Promise<T>;
+}
+
+export function useDashboardData(): UseDashboardDataResult {
+  const [data, setData] = useState<DashboardData | null>(null);
+  const [loading, setLoading] = useState<boolean>(true);
+  const [error, setError] = useState<string | null>(null);
+
+  const fetchData = useCallback(async () => {
+    setLoading(true);
+    setError(null);
+
+    try {
+      const [updates, metrics] = await Promise.all([
+        fetchJson<JobUpdate[]>(`${API_BASE}/updates/latest/`),
+        fetchJson<DashboardMetrics>(`${API_BASE}/updates/metrics/`),
+      ]);
+      setData({ updates, metrics });
+    } catch (err: unknown) {
+      const message =
+        err instanceof Error ? err.message : "An unknown error occurred";
+      setError(message);
+    } finally {
+      setLoading(false);
+    }
+  }, []);
+
+  useEffect(() => {
+    fetchData();
+  }, [fetchData]);
+
+  return { data, loading, error, refetch: fetchData };
+}