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/shared/lib/utils.ts

@@ -0,0 +1,6 @@
+import { type ClassValue, clsx } from "clsx";
+import { twMerge } from "tailwind-merge";
+
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs));
+}