Initial commit with Phase 0 Scaffolding

frontend/src/app/App.tsx

@@ -0,0 +1,23 @@
+import { Routes, Route, Navigate } from 'react-router-dom'
+import { LoginPage } from '../pages/LoginPage'
+import { HomePage } from '../pages/HomePage'
+import { EditorPage } from '../pages/EditorPage'
+
+/**
+ * Root application component with route definitions.
+ *
+ * Routes:
+ * - /login — password entry / first-run setup
+ * - / — home page (recently edited, library, trash)
+ * - /editor/:id — PDF editor workspace
+ */
+export function App() {
+  return (
+    <Routes>
+      <Route path="/login" element={<LoginPage />} />
+      <Route path="/" element={<HomePage />} />
+      <Route path="/editor/:id" element={<EditorPage />} />
+      <Route path="*" element={<Navigate to="/" replace />} />
+    </Routes>
+  )
+}