feat(01-04): create WizardContext provider and wire into App

- Create src/store/context.tsx: WizardContext, WizardProvider, useWizard hook
- useWizard throws if used outside WizardProvider (prevents silent undefined state bugs)
- Update src/App.tsx to wrap content in WizardProvider
- npm run build exits 0 with no TypeScript errors

src/App.tsx

@@ -1,7 +1,12 @@
+// src/App.tsx
+import { WizardProvider } from './store/context';
+
 export default function App() {
   return (
-    <div className="p-4">
-      <h1 className="text-2xl font-bold">Ready2Blob</h1>
-    </div>
+    <WizardProvider>
+      <div className="p-4">
+        <h1 className="text-2xl font-bold">Ready2Blob</h1>
+      </div>
+    </WizardProvider>
   );
 }