♻️ refactor: implement Phase 1 folder-pattern compliance

- Rename App.tsx to app.tsx (kebab-case naming convention)
- Add barrel exports (index.ts) for src/hooks/
- Add barrel exports (index.ts) for src/components/dialogs/
- Add barrel exports (index.ts) for src/components/layout/
- Update renderer.tsx import to use lowercase app.tsx

This is Phase 1 of folder-pattern.md compliance: establishing proper
file naming conventions and barrel export patterns.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/ui/src/app.tsx

@@ -0,0 +1,35 @@
+import { useState, useCallback } from 'react';
+import { RouterProvider } from '@tanstack/react-router';
+import { router } from './utils/router';
+import { SplashScreen } from './components/splash-screen';
+import { useSettingsMigration } from './hooks/use-settings-migration';
+import './styles/global.css';
+import './styles/theme-imports';
+
+export default function App() {
+  const [showSplash, setShowSplash] = useState(() => {
+    // Only show splash once per session
+    if (sessionStorage.getItem('automaker-splash-shown')) {
+      return false;
+    }
+    return true;
+  });
+
+  // Run settings migration on startup (localStorage -> file storage)
+  const migrationState = useSettingsMigration();
+  if (migrationState.migrated) {
+    console.log('[App] Settings migrated to file storage');
+  }
+
+  const handleSplashComplete = useCallback(() => {
+    sessionStorage.setItem('automaker-splash-shown', 'true');
+    setShowSplash(false);
+  }, []);
+
+  return (
+    <>
+      <RouterProvider router={router} />
+      {showSplash && <SplashScreen onComplete={handleSplashComplete} />}
+    </>
+  );
+}