NextGraph integration (WIP), broker banner, and feature-based architecture

- Add NextGraph data layer with @ng-org/orm, SHEX shapes (Event, UserProfile,
  Participation), session management, and FestipodDataContext with dual-mode
  operation (connected via NextGraph or local seed data)
- Add BrokerBanner and NgStatus components showing connection status
- Refactor to feature-based architecture: organize code by business domain
  (event, user, home, auth, workshop, meeting, notification) instead of
  technical layer. Modules only import from shared/, never from each other
- Collocate BDD features and step definitions with their modules: event-specific
  steps in event/steps/, user steps in user/steps/, shared generic steps remain
  in shared/steps/
- Set up multi-layer BDD structure (frontend/backend/e2e steps per module)
- Add project documentation (AGENTS.md, .project/knowledge/)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/frontend.tsx

@@ -0,0 +1,26 @@
+/**
+ * This file is the entry point for the React app, it sets up the root
+ * element and renders the App component to the DOM.
+ *
+ * It is included in `src/index.html`.
+ */
+
+import { StrictMode } from "react";
+import { createRoot } from "react-dom/client";
+import { App } from "./App";
+
+const elem = document.getElementById("root")!;
+const app = (
+  <StrictMode>
+    <App />
+  </StrictMode>
+);
+
+if (import.meta.hot) {
+  // With hot module reloading, `import.meta.hot.data` is persisted.
+  const root = (import.meta.hot.data.root ??= createRoot(elem));
+  root.render(app);
+} else {
+  // The hot module reloading API is not available in production.
+  createRoot(elem).render(app);
+}